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n 

32X 


1 

2 

3 

4 

5 

5 

'^""^M^WMll 


.  I 


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V 


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NOTES 


ON  THE 


NOKTH  AMERICAN  GANOIDS, 


AMI  A,    LEPIDOSTEUS,    ACIPENSER, 


AND    POLYODON, 


WITH  THIlK(rl'LATS8, 


BY  BURT  G.  WILDER.  M.  D., 

FB0FE8SOA  OF  COMPABATIVB  AXATOMY  AND  ZOOLOaV  IN  THK  CORNBM. 
UNIVKUMTY,  ITHACA,  N.Y. 


tFrom  the  Proceedings  of  the  Ainerii-an  Association  for  O^e  Advancement  of  Science, 
Detroit  Sleeting,  Angnst,  1676.  u 


SALEM,   MASS. 

IfRIN'TKD  AT  THK  SALKM   PRK88. 

■.■^:^;\'/  ■    1876. 

For  sale  by  the  Naturalists'  Agency,  Salem,  Maes.   Pbice  50  Ct8. 


\ 


/' 


A 


V 


h 


ff 


.tdH^  ,^t     V 


I 


CONTENTS. 


FA»a 

I.    The  respiratory  actions  of  Amla  and  Lepidosteus.  151 

II.    The  transformatl<  ms  of  the  tall  of  the  gar-pike  Lepldosteus.  158 

III.  The  transformations  of  the  pectoral  flns  of  Amla  and 
Lepidosteus 1^* 

IV.  The  brains  of  Amla,  Lepldosteus,  Aclpensor  and  Polyodon.  168 

.        .  189 


\ 


-^■««««ysi.i^-y^^->'  <:^^s^. 


-■^i^^lfttimm 


#st4J^^Mjf ,_-  -^  i^im^^  [*..,  —.* 


V 


J0   It  _V^,_.,ir,, 


'?B#«'i- 


B.      NATURAL   HISTORY. 


»t 


.iff" 


Notes  on  tiik   North  Amkkicam  Ganoids,  Amia,  Lkp:do9TEU8, 

ACII  KNSKK  AND  ToLYODON.       Hy  IJUIIT  G.  WiLDEH,  Of  Itlmca, 

N.  Y. 

(With  three  plutci.)     > 

I.  —  The  respiuatory  actions  ov  Amia  and  Leimdosteus. 

The  respirntory  uctions  of  Lepidosteus  liavo  been  iloscribed  by 
Prof.  L.  Agivssiz  and  by  Prof.  Pocy.  Tlie  observations  of  the 
latter  (27)'  arc  reproduced  by  Dnmcril  (4,  II,  30G). 

Prof.  A<j;assiz'  fcinurks  are  reported  us  follows : 

"This  llsli  is  also  reiniirUable  for  tlio  largo  quantity  of  air  which 
escapes  fiom  its  mouth.  The  source  of  this  Prof.  Agassiz  had 
not  been  able  to  determine.  At  certain  times  it  approaches  the 
Burface  of  the  water  and  seems  to  take  in  air,  but  he  could  not 
think  that  so  large  a  quantity  as  is  seen  adhering  in  the  form  of 
bubbles  to  the  sides  of  the  gills,  could  have  been  swallowed,  nor 
could  he  suppose  that  it  could  be  secreted  from  the  gills  them- 
selves" (2). 

During  the  past  summer  the  ten  young  Lopidosteus  mentioned 
in  another  part  of  this  paper,  were  observed  by  me  for  about 
three  weeks.  They  seemed  to  prefer  keeping  rear  the  surface, 
probably  for  convenience  of  aiirial  respiration.  In  emitting  the 
bubble  of  air  they  raised  the  anterior  end  of  the  body  a  little,  but 
I  could  not  be  sure  tliat  they  intentionally  protruded  the  head 
from  the  water.  At  the  same  moment  the  whole  body  was 
suddenly  rolled  on  one  side,  and  one  or  more  bubbles  of  air  es- 
caped from  the  mouth.  Within  a  second  or  two  after  assuming 
the  horizontal  po-jltion,  other  and  smaller  bubbles  escaped  from 
the  opercular  oriiice. 

With  the  smallest  gar  (G-S"""-,  about  2^  in.  long),  these  respiratory 
movements  occurred  pretty  regularly  at  intervals  of  ^  to  J  of  a 
minute.  It  rolled  almost  invariably  upon  the  right  side  so  as  to 
emit  the  bubbles  from  the  left.  The  ordinary  branchial  respiratory 
movements  of  the  jaws  and  opercula  were  95  per  minute. 

Very  often  these  young  individuals  of  L.  osseris,  and  more  fre- 
quently the  adults  of  the  smaller  species  (L.  platystomus),  would 
protrude  the  snouts  from  the  water  in  the  respiratory  act ;  but  the 

>  See  Hat  of  works  referred  to,  at  the  end  of  this  paper.  The  firs';  flgnre  desig- 
nates Uie  number  of  the  work  outhe  list;  the  last,  the  page;  themiddle,  when  it  occurs, 
the  volume. 


h 


152 


B.      HATUHAL  IIISTOHT. 


.       lonfTth  of  tho  Jaw,  made  it  impoHsil.Io  to  dotormino  whether  this 

Ina8,„„ch,  however,  as  tho  exhalation  oouhl  bo  ns  well  accomp. 
I'Hl.cl  at  any  depth,  tho  uniform  approach  of  tho  gars  to  Z 
«urn.co  goe«  to  show  that  air  is  taken  in  as  well  as  ,iv!n  out 

More  sat,  (uctory  observations  npon  this  point  were  m..lo"»non 
«c  ult  a„.l  nn,„iured  individnals  of  the  .nu.I-,Lh,  ArrJa,  win  ,  ^ko 
I^p.lo.eu.h.,.  a  very  cellnlar  an.l  vasonlar  air-blad.lor  with  arce 
au-dnct,  and  npon  tho  respiratory  actions  of  .*|uch  noil  .  Z! 
been  published  so  far  as  I  am  aware.  ° 

Amia  seoms  to  prefer  the  darker  parts  of  tho  nqnarinm  and  to 
roma,n  a  ornear  tho  bottom,  but  like  Lrpi.osteusl  co  Ito  tho 
surface  at  .ntervals  to  breathe.     One  or  two  very  largo  b  I  ,^es  of 

jr^e^r. '"""""  -'  -  — '.  -0  losserr: 

twn?i','  "n  ??  '"'■'''''  '•''  '"''^■^'"^"*  «'■  ^''«  J-^^"  ^^^'"cd  to  be 
two-fold,  first  to  permit  tho  escape  of  air,  an.l  second  to  take  in  a 

The  following  method  was  adopted  for  determining  this  point. 

lie  fish  was  gradually  accuslon.ed  to  the  contact  of  tho  Id 
gen  ly  en.brac  ng  the  body  at  about  tho  middle.     After  a  ti    e 
would  sw.m  slowly  in  the  tank  with  no  apparent  agitation  o    a 
count  of  tho  contact,  and  como  to  tho  surface  at  the  usual  into  va  s 
to  discharge  a  bubble  of  air. 

an^ft-o'^at'l"  ";"\P^!Pr''  ^he  Ash  was  permitted  to  move  to 
.Z,Tr  ""'  ""'"'"'  """^  "'^«''  ^  ^^^  not  ve  y  violent 

to'rs:tcr '^ ''"'''  ^™'^^'  ^  ^^'^^  '^'^^^  «^  «^^  -^'^'^  -« 

J,ih',"'  'f'''''"  """"^  "^^   '^  '■'^""■^^^  ^«  ™«y  «"PP08e  that  it 
wo.  Id  have  boon  content.     On  tho  contrary,  after  a  second  or  two 
01   lu.et  (perhaps  resulting  from  the  habit  of  being  satisfied  after     ' 
tho  respuatory  action),  tho  fish  became  n^oro  and" more  une^  y 

a  1  and  finally  escaped  from  the  hand.  It  rose  at  once  to  the 
surface,  and,  wUhont  emHting  any  bubble  whatever,  opened  tkejat^ 
widely  and  apparently  gulped  in  a  large  quantity  of  air.    lluZ 


M3.      _    .'0. 


-€» 


.%.'^LM.  J— .-*i^  ??;•."*•♦« '-I-j.^ 


\ 


iiino  whctlicr  tliia 
as  well  UH  of  ex- 

I  ns  wol!  n<'c'omp- 
tlio  gars  to  the 
s  given  out. 
were  mmlo  upon 
imia,  wliifli,  like 
liuldor  with  large 
licli  iiotliiiig  1ms 

nqimrium  nnd  to 
)  it  comes  to  the 
large  bubbles  of 
OHIO  lesser  ones 

■8  scemerl  to  be 
Jntl  to  take  in  a 
ted  that  I  could 

ing  this  point, 
ct  of  the  hand, 
After  a  time  it 
agitation  on  ac- 
i  usual  intervals 

ted  to  move  to 

but  prevented 

ot  very  violent 

'  air  which  rose 

nppose  that  it 
second  or  two 
satisfied  after 
more  uneasy ; 
lashed  with  its 
it  once  to  the 
pened  the  jaws 
'air.    It  then 


B.      MATURAI.   IIISTOnr, 

descended  and  remained  quiet  for  the  usual  interval.  This  exper- 
iment was  several  times  repeated,  always  with  the  same  result. 

There  seems  no  doubt  from  the  above,  that  with  Amia  there  Is  a 
true  inspiration  as  well  as  expiration  of  air.  The  same  may  be 
considered  [)robable  though  not  yet  proved,  with  Ltpidosteua. 
The  escaping  air  should  be  chemically  examined.  But  there  can 
be  little  doubt  that  in  these  two  genera,  in  Poh/pferua,  and  in  the 
Dipnoans,  all  having  cellular  and  vascular  air-bladders,  there  is 
effected  an  interchange  of  oxygen  and  carbonic  acid,  as  in  the 
lungs  of  aerial  Vertebrates. 

Amia  and  Lepidoateua  have  no  spiracle  and  it  is  small  in  Polyp- 
terxia.  The  three  genera  have  the  space  between  the  rami  of  the 
lower  jaw  occupied  (by  plates  or  folds  of  skin  with  underlying 
muscle)  so  as  to  better  prevent  the  egress  of  air  than  would  be  the 
case  with  most  Teleosts.  But,  as  already  stated,  some  air  escapes 
from  the  opercular  orifice  of  Amia  and  Lepidoateua  after  th.  llsh 
has  descended,  and  while,  probably,  the  air  is  being  forced  back- 
ward so  as  to  enter  the  air-duct. 

Amia  and  Lepidoateua  were  observed  to  perform  the  acts  of 
respiration  above  described  more  frequently  when  the  water  wag 
foul  or  had  not  been  changed. 

It  was  noticeable  that  they  survived  removal  from  the  water  for 
a  much  longer  time  than  Acipenaer  or  Polyodon,  whose  air-bladders 
are  simple  and  but  slightly  vascular. 

II.  ^  The  TKANSF0RMATI0N8  OF  THE  TAIL   (»F  THE  GAR-IMKE,  Lepi' 

doateua. 

That  the  tail  of  the  young  Lepidoateua  is  unlike  that  of  the 
adult  has  been  observed  by  Prof.  Louis  Agassiz.  But  although 
he  repeatedly  called  attention  to  the  transformation,  little  notice 
has  been  taken  of  it ;  it  is  not  mentioned  in  any  systematic  work 
in  the  English  language. 

This  neglect  may  have  been  due  partly  to  the  absence  of  figures 
from  Prof.  Agassiz's  descriptions,  and  partly  to  their  brief  and,  to 
some  extent,  contradictory  nature. 

Tlie  observations  of  Prof.  Agassiz  are  here  reproduced. 

"Zadock  Thompson  has  described  a  young  specimen  under  the 

name  of  Lepidoateua  lineatua. I  have  ascertained,  by 

a  scries  of  specimens,  that  the  detached  lobe  formed  by  the  upper 


154 


B.      NATURAL   BISTORT. 


0 


a  distinct  lobe,   h!ZZ    't  m         ''''"'"'*'  '"'•"'"  "'«  '«>^«r  a 
•ncbrane  aWs;„:\r^:,::;^l:;ro;e'.  "'^  Pectora.s  consist  of 

"The  joiing  gar-pifcg  are  rem«ik»hl.  .. 
embryological  clmraotcr,.    The  Zt  !^     ^  possessing  certain 
pralongatlon  of  .l,e  vcrtebj  ttal  ^^'T'"  "'  '"'"  ''  "<' 
n>cnt,  distinct  from  tl,e  ca",  1^1    J,        r"!"""  "'  "  "'"•>■  "'«- 
times  a  vibratory  motioMnvll  nta'rv      1  '^""'  "'""""'J  ""<'  " 

.ot^n,  or  tbe^^  i.se,r.:ii':::r  sir:Cs"  •' '""- "- 

^n.  .ai.  an,  „.  ,,  ^^^rirX- : - 
passage  «r,t  '>'-o.r'i::'i7LVlZZS2  "  '"  ''" 

■rtre'iS'i",'' ""''"""''  "*"  »'"th  re™'""'""' 

place  be,„.tbl  extrlit,;f  tbe    eSr"aT„  r  ™"™  """'"  '" 
anal,  and  tile  vertebral  ^J,.^..-     ™,    ""'  <"'''"»'>.  »s  a  second 

aiong  the  supe.o?btL:t^ira^;t:- J--'^^^  ^ 
sists  until  the  fish  is    200    ^9  ?         .  conformation  per- 

length."     (Agasl,  ^^  57  )'  ^     '"""^*"^'  "'°"*  «  '-*>-)   in 

to  be  a  very  smill  spedmen  but  wf '  I  I  ''  "'^^^  '«  «*«*«^ 
the  figure  and  the  sEessof  1  m  ' ''f  ^'"^  ^'•""^  '"^^  «'-  ^^ 
200-  (about  8  inohe")  "ng.  "'"''  "^'  P''^'^^'^'^  ^' '-«' 

My  own  observations  relate  to  thp  fnrm  ^f  n     .... 
young,  before  it  assumed  the  ehl    .    T        ^'  *^"  '°  ^''^  ^'^''^ 
manner  of  formation  7  be  ea^^^^^^^^^^^^^  ^r''!?  '^  ^^^"'^ '  ^'^^ 
Of  the  filamentary  end  of  the  bod-  "     <^isappearanee 

of  the  adult  fish.  ^ '  '*'  representation  in  the  tail 


the  lower  rays," 

I  of  Lepidoateus] 
m  the  lower  as 
torals  consist  of 
•  .  they  have 
e  micklle  line," 

sessing  certain 
of  these  is  the 
of  a  fleshy  fila- 
ament]  had  at 
stiuct  from  the 

\'0S." 

fin  is  properly 

3ohimn,  a  true 

the  column." 

^gassiz  speaks 
ets,  as  in  the 
the  erroneous 
T  rays." 
'unded  caudal 
iie  caudal  is 
1  as  a  second 
Jtached  lobe, 
rmation  per- 
J  inches)   in 

Jriptions  by 
at  is  stated 
I  the  size  of 
ably  at  least 

in  the  very 
gassiz ;  the 
lappearance 
1  in  the  tail 


**.^■>?■^^ 


.i ._-.  1.:. 


B.      NATURAL   IlISTORT. 


155 


The  material  at  my  disposal  is  as  follows  :— 

A  Young  Lepidosteus  brought  to  me  in  alcohol  by  Master 
Edward  Steers  (nephew  of  the  late  Prof.  Evans  of  Cornell 
University),  who  took  them  from  the  Red  River,  near  Shreveport, 

La.3  X  .    fl     1 

The  smallest  of  these  is  shown  (enlarged  5  diameters)  m  tig.  i. 

It  is  18  millimeters  (about  f  of  an  inch)  long.    The  largest  is 
44™"""  (about  If  inches)  long. 

B  Ten  young  Lepidosteus  (probably  L.  osseus)  obtained  by 
me  in  the  Illinois  River,  at  Peoria,  during  July,  1876.  These  were 
kept  alive  by  me  and  carefully  watched  for  from  three  weeks  to  a 
few  days  each.  The  smallest  is  63"""-  (about  two  and  a  half 
inches)  long;  the  largest  is  300™™'  (about  twelve  inches)  long. 

C  Numerous  specimens  and  preparations  of  adult  and  partly 
grown  L.  osseus  and  L.  platystomus  in  the  Museum  of  the  Cornell 

University.  ..  , 

The  smallest  Lepidosteus  in  my  possession  (it  is  apparently 
much  smaller  than  any  that  have  hitherto  been  examined)  is  18'""- 
(a  little  less  than  three-fourths  of  an  inch)  in  length.  In  figure  1 
it  is  enlarged  5  diameters.     Unlike  most  young  specimens  it  is 

almost  colorless.^  ,  „  i    . 

The  head  is  rather  short  and  depressed  like  that  of  Polypterus. 
The  eyes  are  large  and  dark.  The  nostrils  are  easily  seen ;  the 
anterior  openings  look  upward  and  outward  instead  of  downward 
and  forward  as  in  the  adult.  The  branchiostegal  membranes  are 
separate  as  far  forward  as  the  transverse  fold  which  exists  in  all 

Lepidosteus.* 

The  ventral  fins  have  not  yet  appeared.  The  pectorals  are  very 
large  and*  prominent,  and  consist  of  a  central  lobe  with  a  thin 
border  or  fringe.  The  significance  of  this  will  be  discussed  here- 
after; see  page  166.  ,^  ,    ^u  * 

A  median  fin  extends  from  the  middle  of  the  length  to  the  vent, 

.several  of  these  were  handed  by  me  to  the  late  Prof.  AK""'-  y"-;";'""''**^^ 
hlg  failing  health  and  pressing  avocations  prevented  any  examination  Of  them,  and  they 
have  Ulen  Sy Toan'od  to  me  by  Mr.  Alex.  Agassiz,  Curator  of  tho  Museum  of  Com- 

''Tiws  U  Sr/ase  with  two  small  specimens  aboutB-™  long,  taken  flrom  the  stomach 
of  JsmM  Lepido,teu,.    They  are  probably  newly  batched  gars,  but  are  not  capable 

"MthSS  are  reasons  for  regarding  this  fold  as  homologous  with  the  hinder 
borderTf  tlie  guiar  plate  of  Amia.  But  as  this  question  Involves  the  homology  of 
■ome  other  parts  now  undetermined,  I  reserve  it  for  another  occasion. 


)iiii'iiii»'»»«ii|p«i>»»g(iiM»'W>* 


156 


B. 


NATURAL   niSTOBT. 


and  thence  to  the  end  of  tho  fnii      a    •    -i 
-    «s  aiong  the  hinde 'third  of  t'  ,oXZlZ  '  xT^f  •'"  ^^■ 
deep  and  consists  of  a  delicaf«  rT^K  '  ^"  '^  *J"'*« 

numerous  and  slender  ravs  in  cTol!  '"'  '"^P^*'^^  ^^  ^''y 

backward.  ^       '^°''  apposition  ;  they  incline  slightly 

>lio«r  a  gradual  .|,a„„|„„  „,°;  .  '    ^'"'  '"Kef  specimens 

m.y  Infe?  that   n  Z  ^  ^f  *!,r'''  "'""''^  '*™-  "• 

2- M  —a,  „.:r:i  ;tr  srsr:^: 

They  appear  to  be  somewhat  thiclcpr  fho«  tu^ 
of  the  fin,  and  darker  fromr^L  .         I         ^  surrounding  parts 

Str'-'^'  .an  .e<,e„ea.  r^^^XZ^^Z 

mens.     It  has  no  large  ravs  and   i!!    ™''*^'^  '°  '^'g^r  speci- 
fy possibly  represer  thrser„dlr;Tr;;"^ 
-ore  probably  the  upper  lobe  of  the    audal  fi?^  "S     !? 
Z7:Z:J'''  correspondence  will  be  reLred  L  h^rtlr 
The  spot  (C)  on  the  lower  lobe  of  the  caudal  nf  ti!!      "^^^"f' 
dosteus  is  evidently  a  develoDins  fi„  '''^, ''!"''*/. *>f  ^^^  ^o^^g  ^ei>t- 

of  the  primordial  L.    In  the  cent/e  of  thV.;   f  T  ''''  '''' 
dimlv  seen  four  nr  fi..  i  '^®  thickened  space  are 

and  LokwaS      Their  atTT  T  '""""^  obliquely  downward 

indicated  by  its  ?h^kel?"^>!°  '''  ""^'^  °^  *^«  ^'^y  »« 


^Jk 


.*„.:jfc.i.. 


B.      NATURAL   HISTORY. 


157 


rnordial  fin  ex- 
This  fin  is  quite 
hited  by  very 
I  incline  sJightJy 

I  tliis  specimen, 
fger  specimens 
py.  whence  we 
P'ery  acute. 
otonward  incli. 

either  nearly 

r. 

special  altera- 
opposite  each 
'tejior  to  the 

funding  parts 
n  of  pigment 

y  the  portion 
arge  rays,  or 
>rdial  fin,  are 

'd  hardly  be 
larger  speci- 
ntirely.5    jj 

^cemus;  but 
Undina  and 
h6reaflter. 
^oung  Lepi. 
an  the  rest 
space  are 
downward 
le  body  is 

""gination. 
the  tail  of 
probably 
ted. 

■Dgr  skate  as 
•l«e  before 


The  spociri.  ;  above  described,  represents,  so  far  as, I  am  aware, 
the  earliest  known  stage  of  Lepidoateus.  But  there  can  be  no 
doubt  that  at  a  still  earlier  stage  the  tail  was  simple  and  undiffer- 
entiated like  that  of  Amphioxus. 

A  second  very  small  specimen  is  no  longer  than  the  one  above 
described,  but  seems  to  be  more  developed.  It  is  darker  colored ; 
the  belly  being  almost  black  while  the  upper  half  of  the  body  is 
browjiiiJh.  The  four  median  flns  are  indicated  by  decided  though 
irregular  blotches,  and  the  rays  of  the  infra-caudal  are  more  dis- 
tinct. 

White  longitudinal  elevations  show  where  the  ventral  fins  (  Ve) 
are  about  to  appear. 

The  difference  in  the  color  of  these  two  smallest  specimens  is 
very  marked.  The  white  one  is  apparently  the  younger  although 
a  trifle  the  longer.  But  it  cannot  be  determined  at  present  that 
the  color  is  developed  only  after  the  attainment  of  a  certain  size 
or  stage  of  growth. 

The  specimen  next  figured  (Fig.  2)  presents  the  following  fea- 
tures. Its  length  is  23"'"'-  Its  colors  are  darker  than  the  one  first 
described,  but  less  decided  than  in  the  second  small  specimen  re- 
ferred to. 

The  ventral  flns  (  Ve)  are  little  white  buds  opposite  the  anterior 
extremity  of  the  primordial  fin  (1).  This  latter  has  changed  but 
little.  It  seems  rather  thinner  and  its  borders  are  ragged,  as  if  in 
process  of  removal  by  both  absorption  and  abrasion. 

In  addition  to  the  interruption  for  the  vent,  the  primordial  fin 
now  presents  three  emarginations,  as  follows :  —  1.  About  mid-way 
between  the  spots  representing  the  dorsal  and  the  supra-caudal 
fins.  2.  Behind  the  spot  representing  the  anal  fin.  3.  Between 
the  primordial  fin  (3)  on  the  lower  border  of  the  tail  and  the 
infra-caudal  lobe,  which  now  projects  slightly  and  is  supported  by 
eight  or  ten  rays  split  at  their  tips  but  reaching  the  border  of  the 
fin. 

In  this  specimen  we  see  the  beginning  of  the  changes  which  are 
to  result  in  the  total  disappearance  of  the  tail  proper  and  the 
taking  of  its  place  and  oflSce  by  the  greatly  enlarged  infra-caudal 
lobe. 

Passing  over  intermediate  sizes  in  which  the  head  is  progres- 
sively lengthened,  and  the  ventrals  enlarged  we  come  to  the 
specimen  represented  in  fig.  3. 


'^yff.t,  iwmiii^i|iw*»-<tf' 


.  •y##»  ^l^lC^p  (••iNf9*( 


158 


B.      NATURAL   HISTORT. 


Like  the  one  first  doscribcd  this  is  a  pale  individual.  Its  total 
length  is  44'""''  From  the  tip  of  the  snout  to  the  middle  of  the 
eye,  9"""- ;  from  the  eye  to  the  vent,  21""''- ;  from  the  vent  to  the 
tip  of  the  tail  14""" 

The  primordial  fin  has  disappeared  excepting  on  the  border  of 
the  filament  {Ji)  which  is  the  elongated  and  slender  termination 
of  the  body.  The  pectoral  fins  are  still  distinctly  lobate,  the  thin 
border  not  being  more  than  one-half  as  broad  as  the  fleshy  central 
lobe. 

The  anal  and  dorsal  fins  are  distinct,  and  have  each  seven  rays. 
The  ventrals  are  still  very  small. 

The  rays  of  the  infra-caudal  are  distinct.  They  are  more  nearly 
in  line  with  the  body  than  in  the  younger  specimens,  while  the  tail 
is  slightly  elevated.  Both  the  filament  and  the  infra-caudal  lobe 
have  increased  in  length.  But  the  latter  has  also  become  wider, 
while  the  former  is  so  slender  as  to  merit  the  name  filament.  It 
projects  about  1.5"""-  beyond  the  infra-caudal  lobe. 

The  specimen  last  described  is  the  largest  of  those  from  the 
Red  River.  The  smallest  of  the  specimens  from  the  Illinois  River 
has  a  total  length  of  63"""  ;  13""""  from  muzzle  to  middle  of  eye  ; 
28"™'  from  eye  to  vent,  and  22"""  from  vent  to  tip  of  filament. 

As  in  most  of  the  Red  River  specimens  and  all  of  those  from 
the  Illinois,  the  dark  lateral  stripe  is  strongly  contrasted  with  the 
white  belly  and  brownish  back.  The  border  of  the  pectoral  is  now 
equal  to  the  lobe.  The  tip  of  the  caudal  filament  is  very  slender 
and  projects  S'""'  beyond  the  infra-caudal  lobe. 

At  the  base  of  the  filament,  just  behind  the  tip  of  the  dorsal, 
are  two  pairs  of  slight  elevations,  one  behind  the  other,  and  look- 
ing backward.  These  are  the  first  representatives  of  the  fulcra; 
a  series  of  strong  spine-like  plates  which,  in  the  adult  gar,  cover 
the  anterior  part  of  the  upper  and  lower  borders  of  the  tail. 

In  a  specimen  108"'"'  long,  the  tips  of  the  filament  and  the  infta- 
caudal  lobe  coincide.  Both  have  increased  in  length  and  width, 
but  the  lobe  more  rapidly  than  the  filament. 

The  outlines  of  scales  appear  on  the  sides  of  the  hinder  half  of 
the  body,  and  there  is  an  increase  in  the  size  and  number  of  the 
fulcra. 

In  a  specimen  measuring  142"'"-  from  tip  of  head  to  tip  of  caudal 
lobe,  this  latter  projects  8"""-  beyond  the  filament.  Its  ra3's,  that 
is,  the  central  ones,  are  in  direct  line  with  the  axis  of  the  body, 


1!* 


Jt,   ^^^.„.^m^  i 


I.    .^  :■'"»'  1^— •»■ 


B.      NATURAL   HISTORT. 


150    — 


h'-    Its  total 

'Diddle  of  the 

Pe  vent  to  the 

[the  border  of 
termination 
r>ate,  tJio  tliin 
Iflesliy  central 

I'l  seven  raya. 

"lore  nearly 
vliile  the  tail 
■caudal  lobe 
come  wider, 
i'ament.    It 

se  from  the 

'inois  liiver 

Idle  of  eye ; 

ament. 

tliose  from 
'e<J  with  the 
oial  is  now 
Bi'y  slender 

tbe  dorsal, 
and  look- 
'c  fulcra; 
^ar,  cover 
ail. 

tbe  inft-a- 
id  width, 

'  half  of 
>rof  the 

f  caudal 
J's,  that 
2  body, 


while  the  base  of  the  filament  is  crowded  upward.  There  are 
now  Ave  pairs  of  fulcra,  the  liindermost  of  which  extends  back- 
ward as  far  as  the  point  of  separation  between  tlie  filament  and 
the  lobe.  Behind  tliis  point  the  filament  is  apparently  undergoing 
structural  degeneration  and  removal.  It  is  thin,  slender  and 
ragged  at  the  edges. 

But  there  is  evidently  considerable  variation  as  to  the  period  of 
this  removal.  For  of  two  specimens  about  190"""-  in  length,  one 
has  the  filament  equal  to  the  lobe,  and  in  the  other  it  is  but  3"""' 
shorter. 

Tlie  largest  specimen  in  which  the  filament  is  preserved,  is  about 
800'"'"-  long.  The  lobe  projects  IS"""'-  beyond  the  filament.  The 
free  part  of  the  latter  is  much  attenuated,  and,  during  life,  was 
but  feebly  and  occasionally  employed.  The  tail  of  this  specimen 
is  shown  in  fig.  4. 

In  imagination  we  may  readily  supply  the  stages  intermediate 
between  that  last  described  and  the  tail  as  usually  represented, 
where  the  free  part  of  the  filament  has  wholly  disappeared,  and 
its  base,  covered  by  the  fulcra,  seems  to  form  only  the  upper 
border  of  the  functional  tail.  Tliis  latter,  however,  from  a  mor- 
phological point  of  view,  is  really  an  appendage  of  the  filament. 

The  movements  of  the  filament  have  been  well  described  by 
Agassiz.  He,  however  (2),  speaks  of  it  as  "involuntary."  By 
this  he  may  have  meant  only  that,  as  with  other  very  rapid  vibra- 
tions, a  separate  volition  is  not  required  for  each  individual  move- 
ment. In  fact,  during  vibration,  the  filament  is  invisible.  But 
the  motion  is  not  involuntary  as  is  that  of  cilia  or  unstriped  mus- 
cular fibres.  For  at  times  the  filament  is  wholly  at  rest ;  it  may 
be  elevated  or  depressed,  curved  strongly  to  the  one  side  or  to  the 
other,  and  more  or  less  rapidly  vibrated  in  any  of  these  posi- 
tions. 

The  movenfent  may  be  compared  to  that  of  the  wings  of  most 
insects  and  of  the  humming-bird.  Still  more  closely  with  that  of 
the  tail  of  Crotalusfi 

On  each  side  of  the  cartilaginous  rod,  in  its  whole  length,  is  a 
band  of  striated  muscular  fibre. 

It  would  be  interesting  to  ascertain  whether  the  nervous  supply 
comes  from  the  cord  within  the  filament  or  from  tbe  permanent 

•  Many  of  the  Colubrida,  nnder  strong  excitement,  will  vibrate  tlie  tail  as  does  the 
rattlesnake. 


4i. 


m 


*IIO 


B.      NATURAL  HISTOnT. 


„.  portion  of  the  cord  anterior  to  the  point  of  its  separation  from  the 
infra-eaudal  lobe. 

The  representation  of  the  filament  in  the  adult  tail.  Agassiz' 
figure  of  the  tail  of  Lepidoateus  (5,  tome  II,  tab.  A),  was  prob- 
ably  made  from  a  dry  preparation,  and  his  description  (tome  I, 
part  II,  23),  does  not  mention  any  cartilaginous  prolongation  of 
the  bony  vertebral  column.  I  am  not  aware  of  any  other  figures 
or  description  of  the  tail  of  Lepidosteus. 

Figure  5  represents  (reduced  i)  the  dissected  tail  of  a  medium 
Bized  L.  platystomus.  It  will  be  noted  that  the  ouMine  of  the 
caudal  fin  (the  infra-cau.lal  lobe  of  the  foregoing  descriptions)  is 
nearly  though  not  quite  symmetrical ;  the  lower  rays  being  a  little 
shorter  than  the  uppermost. 

In  the  figures  of  Agassiz  and  Du-.n^ril  the  outline  is  much  more 
oblique.  This  however,  may  be  Jue  in  part  to  the  fact  that  the 
upper  rays  are  usually  less  separated  than  the  lower,  so  as  to 
cover  less  area  than  the  lower. 

Probably  too,  there  is  specific  variation  in  this  respect.  I  am 
inclined  to  think  also  that  the  same  species  presents  different 
characters  at  diff-erent  ages.  But  for  the  determination  of  these 
questions  a  large  number  of  individuals  should  be  compared  after 
their  species  have  been  ascertained.  At  present  the  taxonomy  of 
Lepidoatetis  is  in  a  very  confused  state.' 

The  outline  of  the  base  of  the  fin  presents  a  double  curve  like 
an  elongated  letter  /.  The  fulcra  cover  the  anterior  two-thirds  of 
the  dorsal  border  and  three-fourths  of  the  ventral  border.  Both 
series  are  closely  attached  to  the  uppermost  and  lowermost  caudal 
ray  respectively.  These  rays  not  only  divide  and  subdivide  like 
the  fin  rays  of  Malacopteri,  but  also  consist  of  two  lateral  halves* 
which  are  often  not  exactly  applied  to  each  other,  as  seen  in  fig.  6. 
The  lateral  halves  of  the  uppermost  caudal  ray  are  separated 
from  each  other  excepting  at  their  lower  border,' and  between 
them  lies  a  tapering  cartilaginous  rod,  whose  upper  surface  is 
covered  by  the  bases  of  the  dorsal  fulcra.     The  relation  of  parts 

i»  L^*"^  '""f  **  '""^  '"'  """"y  *"*'®'"  American  forms  which  are  not  readily  obtainable 
ta  large  numbers  by  European  naturalists;  as,  for  instance,  Ihelmerican  Sturgeol 
the  Petromyzontlda),  and  the  tailed  Batrachians.  -"t-ncan  sturgeous, 

rave  of  mplllil';"'  "*^  ?""  Humphrey  (8, 69)  have  called  attention  to  the  fact  that  the 

meSanTlZ''  TJ  '""'"S  f  f  '""'""  ""  '»  """"'Po-"!  to  a  lateral  factor  of  a 
wlee  doub";  '  ""'  '^"' '"  ^'»"*'"«'»  ">«  «y«  of  *•>«  ventral  flna  are  like- 


"^^ 


i*  • 


m.. 


;wii,im*.!^-U-    .r^  '.jmtm'   1^  — 


B.      NATURAL  HMTORT. 


161 


ration  from  the 

fail.    Agassiz' 

»  was  prob- 

iHion  (tome  I, 

[olongation  of 

other  figures 

of  a  medium 
>uMine  of  the 
ascriptions)  is 

l^eing  a  little 

is  much  more 
fact  that  the 
""er,  so  as  to 

aspect.  lam 
3nts  different 
t'on  of  these 
mpaied  after 
taxonomy  of 

'e  curve  like 
two-thirds  of 
>r(ler.     Both 
most  caudal 
Mivide  like 
eral  halves' 
en  in  fig.  6. 
e  separated 
id  between 
surface  is 
•n  of  parts 

ly  obtalnnlile, 
m  Stiirgeoua, 

fact  that  the 
«l8  It  asono 
1  factor  of  a 
lus  aro  like- 


Is  seen  in  flg.  6,  which  represents  a  vertical  section  of  the  upper 
border  of  the  tail  about  the  middle  of  the  series  of  fulcra. 

Posteriorly  the  rod  may  be  traced  to  beneath  the  hindermost 
fulcra,  this  point  corresponding  nearly  with  the  point  of  separa- 
tion of  the  filament  and  infra-caudal  lobe  in  the  young.  Ante- 
riorly it  descends  gradually  to  become  continuous  with  the  hinder- 
most  vertebra. 

The  cartilaginous  rod  above  described  is  called  notochord  by 
Huxley  (7,  20).  A  cross-section,  however,  shows  that  it  really 
represents  the  whole  spinal  axis,  as  seen  in  fig.  6.  The  noto- 
chord (IT)  is  surrounded  below  and  on  the  sides  by  the  cartilagi- 
nous and  unsegmented  basis  of  the  vertebrae  (CS)  which,  above, 
separates  into  two  laminie  enclosing  the  neural  canal  and  the 
spinal  cord  (<SC). 

The  structures  above  described  are  readily  seen  in  the  tail  of 
the  adult  Acipenser  and  Polyodon.  After  maceration  in  weak 
spirits  for  some  months,  the  notochord  of  these  genera  may  be 
withdrawn  from  the  surrounding  cartilage  as  a  membraneous  tube, 
the  contents  of  which  may  be  washed  out. 

In  Polyodon  the  fibres  of  this  membraneous  notochordal  sheath 
are  arranged  in  a  peculiar  net-work  permitting  considerable  exten- 
sion, with  contraction  of  the  caliber,  or  shortening  with  corres 
ponding  increase  in  diameter. 

In  Amia  the  cartilaginous  sheath  is  thicker  in  proportion,  but 
the  true  notochord  and  the  spinal  cord  may  be  traced  to  the 
extremity.  , 

The  whole  structure  is  much  shorter  than  that  of  Lepidosteua, 
but  in  several  specimens  prepared  by  me,  it  comes  much  nearer 
the  upper  border  of  the  fin  than  in  the  figure  by  Huxley,  (7,  fig. 
6).    The  rod  is  not  represented  by  Franque  (10). 

The  tail  of  the  adult  A7nia  has,  therefore,  essentially  the  same 
structure  as  has  that  of  Lepidoateua.  Nothing  is  as  yet  known  of 
'the  earlier  stages  of  its  development.  Through  the  kindness  of 
Prof.  H.  A.  Ward,  of  Rochester,  I  have  recently  obtained  two 
small  specimens,  respectively  70'""-  and  100""-  (about  three  and 
four  inches)  long,  which  have  the  characteristic  tail  of  the  adult^ 

*  These  specimens  will  be  described  upon  another  occasion.  For  the  present  I  will 
only  mention  that  in  both  the  markings  on  the  body  and  flns  are  more  distinct  than  in 
the  adult,  and  that  the  smallest  presents  two  decided  black  stripes  on  each  side  of  the 
head,  one  of  which  runs  across  the  eye,  as  in  the  yonng  Lepidosteua,  while  the  other 
descends  obliquely  backward  fl'om  the  eye  toward  the  margin  of  the  operculum. 

A.  A.  A.  S.  VOL.  XXIV.     B.  (11) 


1' 


■'..  [tm-^mf^^Z'^'^'-^BmSSf^ ' 


1/ 


•.■<*«*iW*W 


I' 


w 


1G2 


B.      NATURAL   IIISTORY. 


I- 


witli  an  even  more  decided  upward  inclination  of  the  upper  caudul 
/•^  rays,  in  strong  contrast  wltli  the  figures  of  Franquo  (10)  and 

Iluxlcy,  (7,  Fig.  G). 

Nevertheless,  so  nearly  docs  the  tail  of  the  adult  Amia  resem- 
ble tliat  of  Lepidosteua,  that  I  cannot  avoid  inferring  that  it 
passes  through  a  similar  series  of  transformations.  And  I  would 
suggest  to  those  who  live  near  the  breeding  places  of  Amia,  the 
importance  of  making  a  complete  study  of  its  development. 

As  the  most  telcostcoid  of  Ganoids  (its  ganoid  nature  being  in 
fact  denied  by  LiJtken,  16,  336),  its  embryology  will  be  especially 
valuable. 

The  stages  through  which  the  Lepidoateus  passes  are  comparable 
with  the  adult  conditions  of  various  living  and  fossil  forms. 

But  this  parallelism  is  rarely  or  never  exact  in  regard  to  more 
than  one  of  the  features  under  consideration,  the  direction  of  the 
spinal  axis  and  tlie  subdivision  of  the  primordial  median  fln. 

As  already  stated  the  first  stage  is  not  represented  among  the 
specimens.  But,  judging  from  all  analogy,  we  may  infer  that  the 
young  Lepidoateus  of  about  10"""-  in  length,  has  a  continuous 
median  fin  with  no  differentiation  of  color  or  thickness^  and  with 
no  sign  of  subdivision  into  separate  fins ;  and  that  the  posterior 
end  of  the  body  is  horizontal  or  sliglitly  deflected  downward, 
separating  the  equal  or  nearly  equal  upper  and  lower  caudal  lobes. 

In  the  earliest  of  the  stages  here  described  the  spinal  axis  is 
still  nearly  horizontal,  but  the  median  fin  shows  signs  of  subdivision. 

In  both,  the  tail  would  be  described  as  truly  homocercal  by  most 
authors,  as  aiphycercal  by  McCoy  and  Uuxley,  and  as  protocercal 
by  Wyman. 

I  do  not  wish,  on  this  occasion,  to  discuss  the  general  subject  of 
the  nomenclature  of  tails.  But  it  seems  to  me  that  all  the  argu- 
ments of  Huxley  in  favor  of  diphycercal  for  homocercal"*  as 
applied  to  tails  like  that  of  Polypterus,  apply  with  even  greater 
force  toward  substituting  protocercal  for  both.  For  the  latter 
term  indicates  that  the  structure  under  consideration  exists  in  the 
earliest  known  stages  of  development  of  Selachians  and  Ganoids ; 


><>  Cope  (17)  has  proposed  "  isoceroal "  for  the  Bame  form  of  tail.  But  he  applies  this 
term  to  tiie  eel  (.Anguilla),  in  whicii,  according  to  Uuxley  (IS,  42),  the  arrangement  is 
really  heterocercal  aa  in  most  if  not  all  other  osseous  flshes.  Tlie  whole  subject,  tiow- 
ever,  needs  a  special  revision  by  comparison  of  several  stages  of  development  of  the 
tail  in  all  forms  of  aquatic  vertebrates. 


I 


>."•-. 


,^ 


J — 


B.     NATUUAI,  iiisTonr. 


163 


•n  of  the  upper  camJul 
'f  Fianquo  (lo)  and 

»c  adult  Amia  rcsem- 
3ul  inferring  that  it 
^tions.  AndlwoulU 
places  of  Amia,  the 
'  <lf  velopment. 
loid  nature  being  in 
gy  will  be  especially 

isses  are  comparable 
I  fossil  forms. 
'•  in  legard  to  more 
tlie  direction  of  the 
iai  median  fin. 
esented  among  the 
may  infer  that  the 
has  a  continuous 
liickness^  and  with 
tliat  the  posterior 
fleeted  downward, 
3wer  caudal  lobes.' 
tl»e  spinal  axis  is 
jns  of  subdivision, 
mocercal  by  most 
nd  as  protocercal 

reneral  subject  of 
hat  all  the  argu- 
homocercal'o  as 
ith  even  greater 
For  the  latter 
ion  exists  in  the 
»s  and  Ganoids ; 

But  he  applies  this 
.  the  aiTmifrement  ig 
whole  subject,  liow- 
development  of  the 


In  certain  very  nnclenl  Ganoids  (as  Ghjptolo'mus  and  GurnptijchiuH)  ; 
and  in  tJie  generalized  forms  Lppldosiren  and  Ceratodua. 

1  have  not  been  al)le,  however,  .to  find  tlie  word  used  clsewhcro 
than  in  Wyman's  paper  on  the  Development  of  Jtaki  hutii*  (11). 

Upon  the  general  subject  see  Huxley  (6,  7,  and  15),  with  other 
papers  therein  referred  to. 

This  stage  of  tiie  Lepidonteus  may  be  compared  with  Amphioxua, 
the  lowest  known  Vertebrate,  with  Lepidosiren,  Protopterus  and 
feratoc/KS,!'  where,  however,  the  primordial  ttn-rays  seem  to  imve 
been  replaced  by  stronger  and  permanent  rays  ;  Myxine,  Bdellos- 
toma  and  Petromyzon,  where  the  rays  are  cartilaginous  ;'■»  (in  some 
species  of  Petromyzon  the  median  Hn  is  continuous,  with  slight 
undulations  indicating  the  subdivisions  in  other  species)  ;  and 
with  Membranchvs  and  Menopoma,  where,  as  in  the  larvae  of 
Anoura,  there  are  no  fln-rays  at  all. 

The  cartilaginous  prolongation  of  the  vertebral  colump  of  Polyp- 
tents  is  not  shown  by  Agassiz  (5, 11,  tab.  C).  It  is  figured  by 
Huxley  and  described  (7,  20),  as  hardly  at  all  bent  up. 

In  a  Calamoichthys  in  my  possession  a  line  drawn  vertically 
across  the  tail  over  the  end  of  the  cartilaginous  rod  intersects 
twelve  fin-rays.  Four  of  these  lie  above  the  rod  and  eight 
below.  Still  the  upward  inclination  of  the  rod  is  very  slight, 
'  perhaps  not  enough  to  prevent  the  recognition  of  these  two  genera 
as  protocercal.  Some  other  form  would  have  been  better,  however, 
for  illustration. 

Among  fossil  forms  with  apparently  protocercal  tails  are  proba- 
bly included  the  extinct  species,  of  Ceratodua  described  by" 
Newberry  and  Cope. 

In  all  the  above  excepting  Polypterus  and  Calamoichthys,  the 
median  fin  is  continuous  as  if  formed  by  direct  enlargeme:  t  of  iLa 
whole  primordial  fin. 

But  in  other  fossil  forms,  as  in  the  two  genera  above  named, 
parts  of  the  primordial  fin  are  difierentiated  and  bear  the  names 

dorsal  and  anal. 

The  most  instructive  of  these  is  Olyplolcemus,  a  Devonian  fish 
described  and  figured  by  Huxley  (6,  fig.  1,  and  plates  I  and  II). 
"There  are  two  dorsal  fins  placed  in  the   posterior  half  of  the 

n  Commonly  known  as  Dipnoans,  but  Included  among  the  Ganoids  by  GUnther  (10) 
Gin  (11!)  and  others. 

u  Perfectly  distinct,  although  these  have  been  called  Dormoptev!  by  Owen. 


. 


I 


V^i' 


'Li.i- 


I  t** 


\U 


B.      NATURAL   IIISTORT. 


"/ 


',1        I 


.//  / 


bofly.  Tho  ventral  fins  are  situated  under  tlic  first  dorsal  and  aro 
succeeded  by  n  single  anal.  Tiio  cau<lnl  fin,  whose  contour  is 
rhoinboidal,  is  divided  into  two  equal  lobes  by  tiic  prolonged  coni* 
cal  termination  of  tl»e  body ;  in  other  words,  the  fish  is  diphycer- 
cal  or  truly  hoinocercal"  (Huxley  G,  3). 

Huxley  states  that  the  head,  body  and  fin,  of  Oyroptycldus  might 
be  described  in  the  terms  wliicii  have  just  been  applied  to  Glyp- 
toUemuH. 

Hotli  these  genera  are  comparable  with  the  first  stage  of  Lepidoa- 
teus,  Tlie  tail  is  strictly  protocercal  (or  "diphycercal").  More- 
over there  are  two  dorsals.  If  tiic  anterior  be  the  homologuo  of 
the  single  dorsal  of  the  adult  Lepiditstetm,  then  tho  posterior  may, 
perlinps,  represent  a  development  of  the  transitory  posterior  dorsal 
of  tlie  j'oiing  LcpidostetiH.  If  the  anals  correspond  in  the  two, 
then  the  infra-caudal  lobe  of  IjopidonleuH  is  not  differentiated  from 
the  rest  of  tlie  tail  in  GUjptolcemns,  or  Oyroptychiua. 

But  it  may  bo  that  anotlier  interpretation  is  more  nearly  correct. 
Certain  otiier  fossil  forms,  as  Undina,  and  probably  Macropoma, 
have  a  continuation  of  the  vertebral  column  between  tlie  two  equal 
lobes  of  the  caudal  fin,  and  the  prolongation  of  the  caudal  extrem- 
ity beyond  it  as  a  filamentary  appendage  (Huxley  C,  15).  Leaving 
out  of  the  comparison  the  advanced  anterior  dorsal  of  Undina, 
the  posterior  dorsal  niaj'  be  compared  with  the  true  dorsal  of  Lepi- 
dosteua;  the  anals  are  apparently  homologous.  There  are  then 
an  upper  and  a  lower  caudal  lobe  of  nearly  equal  size,  the  filament 
projecting  between.  Tho  lower  lobe  may  naturally  be  homologized 
wit'.i  the  permanent  infra-caudal  of  Lepidoateua,  while  tho  upper 
lobe  represents  a  similar  development  of  the  transitory  appearance 
(X)  of  Lepidostens. 

Which  of  these  interpretations  is  correct  will  hardly  be  deter 
mined  before  the  general  afl^nities  of  all  these  forms,  fossil  and 
living,  are  better  understood  than  at  present.  Meantime  I  venture 
to  call  attention  to  the  facts,  well  known  but  not  always  borne  in 
mind,  that  all  median  fins  are  differentiations  of  a  single  continuous 
primordial  fold ;  that  even  in  nearly  allied  forms  they  present 
considerable  diversity  of  size  and  position  ;  and  t'.iat  no  such  tax- 
onomic  significance  is  probably  to  be  assigned  to  them  as  to  the 
lateral  fins,  of  which  there  are  never  more  than  two  pair. 

Leaving  out  of  the  comparison  the  degree  of  subdivision  of  the 
median  fin,  the  stages  8,  4,  and  5,  represented  in  figs  2,  S,  and  4, 


flrst  dorsal  nnd  are 

|)<  whose  contour  i« 

'  tlio  prolonged  coni- 

|tho  flail  ig  dipliyccr- 

OijrnptycluHs  might 
[en  applied  to  Uhjp. 

•8t  stage  of  Lepklog. 
'hycercal").     More- 

0  the  homologiio  of 

1  the  posterior  may, 
ory  posterior  dorsal 
M|iond  in  the  two, 

liOerentiated  from 
chiua. 

nore  nearly  correct. 
Jbably  Macropoma, 
iween  the  two  equal 

the  caudal  extrom- 
'■y  C,  15).     Leaving 

ilorsal  of  Undina, 
rue  dorsal  of  Lepi- 
I.  There  are  then 
il  size,  the  filament 
lly  be  homologized 
»,  while  the  upper 
tisitory  appearance 

I  hardly  be  deter 
forms,  fossil  and 
eantime  I  venture 
'  always  borne  in 
single  continuous 
'ms  they  present 
^!iai  no  such  tax- 
0  them  as  to  the 
ivo  pair, 

ibdivision  of  the 
figs  2,  3,  and  4, 


X>  .a^  -mmr  •rr  • 


-».^-^ 


,■*>■■ 


B.      NATURAL   HISTOnT. 


16A 


have  their  more  or  less  accurate  counterparts  among  various  living 
and  fossil  Ganoids  and  Simrks.'^ 

Alo})iiiii  has  a  long  upper  lobe  (so-called).'* 

In  Pohjndnn  and  some  species  oi  Ar.lpvnuer  and  In  most  Sharks, 
the  upper  lobe  is  but  little  the  longer ;  in  iMtnna  the  lower  lobe 
nearly  ei|ual8  the  upper.  I  am  not  acquainted  with  any  Ganoid  or 
Selachian  where  tiin  lower  lobe  is  the  longer,  as  in  the  sixth  stage 
of  LcpiiloHleus  (Fig.  5).'* 

The  last  stage  (7,  fig.  G),  exists  in  Amla  olone  among  living 
Ganoids,  and,  so  far  as  I  am  aware,  is  not  presented  by  any  palae- 
ozoic forma ;  their  tails  being  either  protocercal  (as  in  Olyptolce- 
mu.t)  or  obviously  heterocercal  as  in  Pulceoniscus,  etc. 

But  among  mcsozoic  forms  the  amioid  tail  is  not  unusual ;  and 
a  series  may  easily  be  formed,  as,  for  instance,  of  Lepirlotua,  Meg- 
alnrun  and  Thviiianpa  by  which  the  truly  heterocercal  tail  is  appar- 
ently converted  into  the  apparently  homocercal  form.  Indeed  the 
tail  of  Mpgalurua,  as  figured  by  Agassiz  (5,  tab.  K,  fig.  4),  might 
almost  be  tauen  for  that  of  Amia.^'^ 

"  Several  (<i)e<^lcs  of  Loricnrid  liiivo  the  n|i|icr  onnilnl  rny  jrronlly  prolonged  »o  ai 
torurm  n  flliinuMif.  In  nn  iidiill  exiimlncil  by  mo  tlicro  ii  no  prolongiition  with  It  of  tho 
notoi'lioril.  It  would  ho  intcrothit;  to  oxamlno  tlio  yonng  in  this  gvnug.  The  fliiimont 
ncldx  another  to  tho  analoKles  between  the  UoniodonlH  of  South  America  and  tho  Stur- 
gconH  or  tho  Northern  hcmlHphere  whiuh  liavo  been  pointed  out  by  AgitHslz  ('20,  30;  31, 
2I2,3!IU;  2-j. :»». 

■*  1  UNO  tho  '.drm  upper  lobo  bORaiiso  it  Ib  commonly  employed.  Strictly  iipeaking, 
however,  it  !»  not  a  lobe  of  tho  caudal  lln  in  any  such  senne  as  is  the  lower  lobe  here 
caliei!  iiiiVa-caudul.  It  is  tho  prolongMtion  ol  tlio  body  and  Is  really  nglgnntiu/Kamrat. 
The  tall  of  Chimera  Is  even  more  exaggerated. 

SoinuUiing  like  a  reversed  representation  of  tho  changes  in  tho  tail  of  Lepidotteu* 
occurs  with  tiie  developing  skate.  Tho  dorHats  of  liaia  bntit  were  found  by  Wyman 
(II,  4:1}  to  "change  ponlttoii  from  the  middle  to  the  end  of  the  tall.  At  tho  time  of 
hatching,  however,  there  la  etlll  a  ^lender  terminal  portion  of  the  tail  wliicii  is  alter- 
wardtt  cither  absorbed  or  covered  up  by  the  enlarged  dorsals  as  they  extend  backward." 

In  a  young  skate  taken  from  the  egg-case  and  measuring  TO"™-  In  length,  I  And  pro* 
Jccting  beyond  tho  second  dorsal  a  slender  lllament  about  lO"'*-  long,  whiuh  is  atrophied 
B8  compared  with  the  rest  of  the  tail,  and  apparently  in  process  of  removal.  (In  Urap- 
tera,  as  remarked  by  Wymun,  this  slendor  tail  is  per»ictent).  Ador  Its  removal  the 
hinder  dorsal  of  tho  skate  occupies  toward  tiie  end  of  the  body  tho  same  position, 
morphologically,  as  if  it  were  a  supra-caudal  lobe  or  dilTerenttation  of  the  primordial 
fln,  uonespondlng  to  the  infra-caudal  lobe  of  Lcpidosteus.  The  end  of  the  vertebral 
column  is  not,  however,  bent  downward  so  as  to  allow  the  dorsal  to  be  strictly  termi- 
P'il :  perhaps  In  adaptation  to  Its  frequenting  tlio  bottom. 

■"  There  seems  to  be  no  reason  why  such  a  form  should  not  exist,  a  reversed  coun- 
terpart of  Alopia»  as  UemirhtimphuB  Is  of  Xiphiat. 

"  In  the  diagrammatic  restoration  of  Ategatiirtu  above  rcfeired  to,  the  scales  are 
represented  as  rhombic.  But  they  are  really  cycloid,  as  lu  Amia,  in  alt  the  four  species 
shown  by  Agassiz  in  Plates  61  and  51*  of  the  same  work.  May  not  Affgalurus  be  a 
fos»^ll  representative  of  tho  Amiadai?  Huxley,  however,  (7,  127),  says  that  "it  is  not 
certain  that  any  member  of  the  group  occurs  in  a  fossil  state;"  and  LUlken  (ll>.  336), 
thinks  "  thoro  is  no  positive  roaaou  for  arranging  the  Mcga'.uri  (whiuh  he  regards  at 
Teleo^toi)  with  the  Amiadie." 


1 


W-: 


'«"»«*f"?»*»^     .: 


'  1 


/ 


1C6 


B.      NATIIHAI,    IIISTonr. 


(  ^ 


'  !    I 


I    ( 


!       / 


Since  I[iixloy(l5)  \\m  sliown  tlin  pioliahility  tlmt  tho  tfills  of 
most  iC  not  all  IVlcoHtci,  iir«  rcully  Htrongly  liclerofciciil,  it  i.s  not 
(lilllcult  to  inm','ino  n  seric»  l)y  wliicli  llie  tiiii  of  AmUi  nIiouIiI  i)0- 
coino  tlmt  or  one  of  tlio  ClnpooiilN  willi  wliicli  Ciivier  iwid  piiiccd 
It.  Indeed  tlicre  ure  CosHil  VtwxwVU  {ThriiMMqiH,  Ax\)U\nrh\ini-hn»^ 
etc.)  wlioso  tailH  ivie  ivj)|)iirontly  ns  peirecliy  lioniocorcal  us  tliosoof 
any  ISalmu  or  Scomber,  hut  wiiicli,  i»y  anuioj^y,  wo  may  snpposo  to 
have  luuMi,  in  tlio  earlier  8tuj,'c«  of  dcvcioptnont,  distinctly  lictero- 
ccrcal,  or,  perliaps,  ev»!n  protoeercal. 

Bnt  the  transition  is  still  i)etter  illustrated  l)y  tlie  ciianges  wliieh 
occur  in  Gtutvrmteuit  as  described  l)y  Huxley  (Ifl)  and  us  lately 
seen  l)y  me  in  a  Siluroid. 

For  in  the  young  Oastprontem  the  cartilaginous  rod  (called  nolo- 
chord  by  Huxley)  is  not  only  strongly  bent  upward  but  also 
reaches  the  upper  angle  of  the  tail,  nearly  as  in  LppMostnm.  Hut 
in  tlie  half.grown  fish,  by  the  growth  of  the  (In  rays  the  end  of  the 
notochord  "  no  longer  reaches,  by  a  long  way,  to  tlio  posterior 
superior  angle  of  the  caudal  tin  ;"  this  is  tho  condition  of  things 
in  Amid, 

It  may  be  saiu,  therefore,  that  the  Teleostcan  tail  does  not  simply 
begin  where  the  Ganoid  tail  leaves  off,  but  actually  overlaps  it; 
the  two  earlier  stages  of  the  former  being  represented  by  the  tails 
of  LepidoHtcua  and  Amia,  the  latter  genus,  as  luis  been  already 
stated,  being  regarded  as  the  most  telcosteoid  of  Ganoids. 

LiJtken  has  remarked  (16,  332)  that  "in  general  an  evident 
progress  from  the  heterocercal  to  the  so-called  homocorcal  or  fun- 
like tail  may  be  observed  running  parallel  to  the  progress  of  tho 
g((ological  epochs." 

The  transformation  of  the  tail  of  Lepidonteus  so  far  ns  already 
known,  would  have  furnislied  an  embryological  parallel  to  the 
structural  and  geological  series ;  while  the  earlier  condition  hero 
first  described  enables  us  to  extend  the  comparison  to  the  proto- 
cercal  forms  of  which  some  are  among  the  oldest  known  fishes  and 
others,  now  living,  are  either  tlie  lowest  of  vertebrates  or  manifest 
such  striking  relations  with  other  classes  as  to  have  received  the 
name  "generalized  Ganoids." 

ill.  —  The  transfoumations  of  the  pectoral  fins  of  Amia  and 
Lepidosteus. 

Raflnesque"  described  a  small  gar-pike  under  the  name  Sarchi- 

>'  Journ.  ac.  nat.  «oI.,  PhUad.,  1818,  vol.  I,  part  11,  p.  418. 


-^.^.^,^, 


r\.: 


,mmr  m-^mA.t^    ^"^^i^M  .^; 


n.      WATURAL   niSTORT. 


117 


lily  tlint  tlio  tnilM  of 
It'lerowical,  it  U  not 
I  of  Amia  nIioiiIiI  l)t>. 
Ill  CiiviiT  IiikJ  pIlKJcd 
I'V'''.  ^ iKpiihirhjindt «/», 
|f)iiioi!crc(il  ««  tlioso  of 
>vc  limy  siii)|»oHc  to 
|"t,  distinctly  lictero- 

'»y  tlio  clinngofl  which 
y  (15)  and  ua  lately 

nils  rod  (called  nolo- 
it  upward  hnt  also 
M  Lppithatum.     \\y\\, 

niys  the  end  of  the 
••^y,  to  the  posterior 

condition  of  tiiingg 

tftil  docs  not  simply 
ictiially  overlaps  it; 
•esentcd  by  tlie  tails 
IS  lias  been  nircady 
of  Ganoids, 
general  an  evident 

Iioniocorcal  or  fan- 
the  progress  of  the 

us  80  far  ns  already 
3al  parallel  to  the 
ilier  condition  here 
•ison  to  the  proto- 
it  known  fishes  and 
Jbrates  or  manifest 
'  have  received  the 

FINS  OK  Amia  and 
the  name  Sarchi- 

%  p.  418. 


run  bccauNO  the  pectorals  consisted  of  a  memlirano  rising  (Voiu  a 
fleshy  lobe. 

Agassiz  (9,  360 ;  8,  5R)  has  shown  that  tills  form  of  pectoral  la 
ciiaractoristic  of  the  young  Lvjiiiti)nteug.  Dumorll  (i,  320)  rpiotos 
Agassiz'  observations  but  makes  no  comment  noon  them.  No 
other  systematic  work,  so  fur  as  I  know,  contains  any  rcferonco  to 
the  fact. 

Since  Iluxloy  (6,  24),  has  proposed  a  now  sub-order  of  Ganoids, 
Crossopterygla,  mainly  "in  consideration  of  the  peculiar  manner 
in  wliicli  the  fin  rays  of  tlio  paired  fins  (tlio  pectorals  and  usually 
tlio  vcntrals)  are  arranged  so  as  to  form  a  fringe  round  a  central 
lobe,"  it  is  desirable  to  ascertain  whotlier  the  early  stages  of  othor 
Ganoids  exhibit  similar  features. 

This  is  certainly  thn  case  witli  all  the  young  Lepidosteus  above 
described,  including  the  largest.  Moreover,  in  any  minute  de- 
scription of  the  adult  L.  platyatomus,  the  pectoral  fins  would  be 
distinguished  from  tho  ventrals  by  the  existence  of  a  dccidod 
fleshy  rounded  lobe  at  their  base. 

In  the  smallest  gar  (Fig.  1,  P)  the  fringe  forms  little  moro  than 
one-third  the  wholo  length  of  the  fln.  As  tho  flsh  grows  the  lobe 
becomes  rather  longer  and  narrower,  but  the  fringe  increases  so 
much  more  rapidly  as  to  render  the  former  comparatively  incon- 
spicuous in  the  adult. 

The  pectorals  of  Amia,  even  the  adult,  have  a  fleshy  lobe.  In 
the  smallest  specimen  already  alluded  to,  the  length  of  the  whole 
fln  is  10"""  and  the  basal  lobe  forms  one-flfth  of  this,  2'""' 

So  far  as  regards  external  form  alone,  both  Amia  and  Lepidos- 
teus must  be  regarded  as  having  lobatc  or  fVinged  pectoral  fins. 

But  the  significance  of  this  fact  depends  largely  upon  two  other 
considerations.  1.  Is  the  structure  of  the  fin  identical  with  that 
of  Polypteru»  and  the  other  forms  included  among  the  Crossop- 
terygia?    2.  Is  the  lobe  necessarily  covered  by  scales? 

It  is  so  covered  in  Polypterv.a  and,  as  I  infer,  in  the  fossil  genera. 
But  I  have  not  found  scales  upon  the  lobe  in  even  the  adult  Amia 
and  Lepidosteus, 

Since,  however,  all  those  forms,  like  the  young  Lepidosteus, 
were  probably  scaleless  when  young,  it  would  seem  that  not  much 
weight  should  be  assigned  to  the  lack  of  scales  in  the  adult. 


,N 


,J. 


0'    jL^J^y 


^«»«»^,^ 


m^ 


<WW  nfYIV- 


168 


IV.- 


B.      NATURAL   HISTORT. 


■On    the  brains  of  Ami  a,  Lepidosteus,  Acipenser  and 
polyodon. 

There  is  a  wide  difference  of  opinion  among  zoologists  respect- 
ing the  limits  of  the  group  commonly  known  as  Ganoids,  and  its 
relations  with  the  other  fishes,  and  the  higher  Vertebrates.  To 
the  group  as  originally  defined  by.  Agassiz  and  Miiller,  including, 
with  many  fossil  forms,  the  living  Lepidosteus,  Polypterus  and 
sturgeons  {Acipenser,  Scaphyrhynchus  and  Polyodon),  Amia  was 
soon  added,  and  Agassiz  was  even  inclined  to  adjoin  the  Siluroids, 
the  Plectognaths  and  Lophobranchs.  Prof.  Gill  (12)  considers 
that  "the  Polypterids  (Crossopterygia  of  Huxley)  and  Dipnoans" 
{Lepidosiren,  Protopterus  and,  probably,  Ceratodus)  exhibit  so 
many  characters  in  common  that  they  are  not  even  entitled  to  sub- 
classical  distinction.  Dr.  Gunther  (19)  considers  the  Dipnoi  as  a 
sub-order  of  Ganoids,  and  unites  these  with  the  Selachians  as  a 
sub-class  of  fishes,  Palseichthyes.  LiJtken  (16)  goes  to  the  other 
extreme  and  excludes  from  the  Ganoids  not  only  the  sturgeons 
but  also  AmiaA^  Cope  (17,  582)  does  not  recognize  the  group 
at  all. 

It  will  be  observed  that,  for  determining  the  limits  and  relations 
of  Ganoids,  naturalists  have  appealed  to  the  scales,  to  the  dermal 
ossifications  upon  the  bead,  to  the  skull  and  skeleton  in  general, 
to  tlie  limbs,  to  the  spiral  intestinal  valve,  and  the  multivalvular 
and  rhythmically  contractile  bulbus  arteriosus. 

The  embryology  of  the  typical  Ganoids  is  wholly  unknown,  and 
this  most  valuable  aid  in  classification  is,  therefore,  not  at  present 
.available. 

The  only  brain  character  which  has  entered  into  the  discussion 
i«  the  cbiasma  of  the  optic  nerves.  In  this  the  Ganoids  differ  from 
the  Teleosts  and  Myzonts,  and  agree  with  the  Selachians  and 
higher  Vertebrates ;  but  the  general  aspect  of  the  brain  is  more 
nearly  that  of  the  Teleosts.  ' 

It  does  not  appear  however  that  any  detailed  comparisons  have 
been  made  between  the  brains  of  Ganoids  and  those  of  other  fishes 
and  the  higher  Vertebrates ;  and  Prof.  Gill  who  alludes  (12)  to 
"  the  superior  taxonomic  value  of  modifications  of  the  brain  and 

>■  LUtken  makes  no  reference  to  the  brain,  and  his  characters  seem  to  be  in  other  re- 
spects defective.  But  (p.  336)  he  admits  the  possibility  that  Aiture  discoveries  max 
some  day  demonstrate  to  us  unknown  bonds. 


"^-mrw- 


.•s^-,»%'^--'^' 


B.      NATURAL  HI8T0RT. 


169 


fS,    ACIPENSER    AND 

zoologists  respect- 
is  Ganoids,  and  its 
r  Vertebrates.    To 

Miiller,  including, 
us,  Polypterus  and 
lyodon),  Amia  was 
djoin  the  Siluroids, 
jrill  (12)  considers 
ey)  and  Dipnoans" 
atodus)  exhibit  so 
ven  entitled  to  sab- 
ers the  Dipnoi  as  a 
he  Selachians  as  a 
)  goes  to  the  other 
only  the  sturgeons 
icognize  the  group 

imits  and  relations 
sales,  to  the  dermal 
celeton  in  general, 
[  the  multivalvular 

lolly  unknown,  and 
fore,  not  at  present 

into  the  discussion 

Granoids  differ  from 

he  Selachians  and 

the  brain  is  more 

comparisons  have 
lose  of  other  fishes 
ho  alludes  (12)  to 
9  of  the  brain  and 

rs  seem  to  be  in  other  re- 
Aiture  discoveries  maj 


i 


heart  in  other  classes  of  Vertebrates,"  does  not  refer  to  any  other 
feature  than  the  optic  chiasma  already  mentioned. 

Having  reasons,««  other  than  those  derived  from  the  extreme 
diversity  of  conclusions  already  referred  to,  for  beUevmg  th«^  a 
Treful  study  of  their  brains  will  throw  light  upon  the  limits  and 
c  a  smcation  of  Ganoids,  I  have  this  summer  (1875)  made  numer- 
ous  preparations  of  the  brains  of  the  four  American  genera  ^m.a,     . 

ZpLLs,  Acipenser  and  Polyodon,  ''^^'"'"iV    V^^T^ 
other  and  with  the  figures  and  descriptions  of  Ganoid  brains  to 

which  I  have  had  access. 

Since,  in  comparison  with  the  preparations,  none  of  the  pub- 
Ush^d  figares  and  descriptions  are  wholly  satisfactory,  I  here  refer 

to  them  in  detail.  . ,   u    •      s=  fi,of  hw 

Apparently  the  earliest  figure  of  a  ganoid  brain  is  that  by 
Stfnn^us  (32)  of  the  sturgeon's  brain.    It  seems  to  be  a  correct 
Representation,  and  fairly  indicates  the  features  which,  according 
to  the  views  I  have  reached,  are  characteristic  of  *he  b-ns  o^  ^ 
Ganoids.    But  no  especial  attention  is  drawn  to  them    and  the 
nomenclature  of  the  two  anterior  pairs  of  lobes  has  not  been  ac- 
cept d  by  later  authors.    Starinius  calls  the  first  pair  from  which 
arise  the  olfactory  nerves,  the  olfactory  tubercles,  and  the  second 
Zv  which  most  authors  call  hemispheres  (but  which  I  believe  to 
rspldllly  developed  portions  of  the  thalami),  the  o^ory  lobes. 
He  ?hus  recognize   no  cerebral  hemispheres  at  all.  and  makes  no 
fomparisou  bfTween  the  sturgeon's  brain  and  those  of  other  fishes, 
nr  the  hisher  Vertebrates.  . 

It  isTbe  noted  that  this  nomenclature  of  the  two  ^ntem^ 
pairs  of  lobes  corresponds  with  that  -WchGottsche  had  applied 
?o  the  brains  of  osseous  fishes,  in  1835.  This  author  30,  445) 
enumerates  the  various  names  which  had  been  given  to  the  hinder 
and  larger  pair,  and  concludes  that  they  are  the  olfactory  lobes, 
the  anterior  paii  being  olfactory  tubercles.  Gottsche  cites  Des- 
moXs  and'serres  as  regarding  the  so-called  olfactory  lobes  as 
Cerebral  lobes,  which  name  has  since  been  more  commonly  em- 
ployed  Gottlche  makes  no  definite  allusion  to  the  brains  of  other 
fishes  than  the  Teleosts.  .    .    ,,v,,i       >  -    t        - 

,0  Based  npon  the  pro.a.Ui^  that  Z^^^^:'^^^^;:^^^^^^,  ^ w^dZl 
from  modifications  by  «f  7' «««^tV^^^!CThe  morcompr;henslve  group. 

rrr^idCiJ^ritrs^errnmbs. 


4t      *,  '-^Ak> 


-^■:  >^..'»H(ii,^.-A.-%,, 


'.  "t";    xrnnifmut 


wm 


I) 


170 


B.      NATURAL  HI8TORT. 


In  1844  Johannes  Miiller  figured  (18)  the  brain  of  Pohjpterua 
from  above,  from  below,  from  the  side  and  in  single  cross  section, 
through  the  pair  of  lobes  next  to  the  anterior. 

There  can  be  no  better  illustration  of  the  slight  importance  as- 
cribed at  that  time  to  the  brain  for  taxonomic  purposes  than  the 
insufficient  of  figures  and  very  brief  des-'ptions,  which  the  great 
ichthyologist  devoted  to  the  brain  of  a  typical  Ganoid.  He  says 
(p.  139)  "Das  Gehirn  der  Ganoiden  ist  eigenthumlich  und  unter- 
scheidet  sich  von  dem  der  Knochenfische  und  Plagiostomen." 
Yet  his  description  of  the  brain  (p.  140)  and  r(imm&  of  the  charac- 
ters (p.  141)  give  us  only  the  optic  chiasma,  a  feature  which  the 
Plagiostomes  share  with  the  Ganoids.     (See  also  41,  24.) 

Miiller  enumerates  the  cerebellum  and  the  optic  lobes,  the 
"lobus  ventriculi  tertii"  (corresponding  to  the  thalamus  of  higher 
vertebrates)  the  hemispheres,  olfactory  lobes  and  olfactory  nerves. 
Although  commenting  upon  the  general  resemblance  of  the  brain 
to  that  of  the  sturgeon  he  does  not  call  attention  to  the  different 
determination  which  he  makes  of  the  two  anterior  pairs  of  lobes. 
In  the  following  year  Busch  (29)  published  figures  of  several 
Ganoid  brains. 

This  work  I  have  not  been  able  to  obtain.  But  if  the  figures  of 
the  brains  of  the  sturgeon  and  the  Chimera,  copied  by  Owen  (24, 
I,  figs.  173  and  179),  are  fair  examples,  the  work  did  not  materi- 
ally advance  the  knowledge  of  either  the  form,  the  structure,  or 
the  homology  of  the  ganoid  brain. 

The  paper  of  HoUard  (34)  admits  three  types  of  brains,  the 
teleostean,  the  plagiostotne  and  the  cydostome.  It  is  not  clear  to 
which  of  these  types  he  would  refer  the  ganoid  brain. 

In  1848,  a  pupil  of  Muller,  H.  Franque,  figured  (10)  the  brain 
of  Amia  from  above  and  below  with  separate  views  of  the  optic 
chiasma.  He  makes  no  comparisons  with  other  brains,  and  his 
description  is  a  simple  enumeration  of  the  lobes  according  to  the 
usual  nomenclature,  the  two  anterior  pairs  being  olfactory  lobes 
and  hemispheres  respectively. 

Dum^ril  (4,  pi.  20),  copies  from  Phillippeaux  and  Vulpian 
figures  of  a  sturgeon's  brain  from  above  and  below.  He  makes  no 
original  observations.  The  so-called  hemispheres  are  shown  as 
solid  rounded  masses  without  eversion  of  the  dorsal  borders,  and 
the  olfactory  lobes  as  solid  without  even  the  orifices  distinctly  por- 
trayed, though  not  interpreted,  by  Stannius  and  Busch. 


■,-».«r,-f*' 


—rfi— .. — ■■•-tri 


^'■•''^>i^ 


B.      NATURAL  HWTORT. 


171 


)rain  of  Polypterua 
ingle  cross  section, 

ght  importance  as- 

purposes  than  tlie 
IB,  which  the  great 

Ganoid.  He  says 
mmlicb  und  unter- 
nd  Plagiostomen." 
ium6  of  the  charac- 

feature  which  the 
JO  41,  24.) 
i  optic  lobes,  the 
thalamus  of  higher 
d  olfactory  nerves. 
)lance  of  the  brain 
on  to  the  different 
'ior  pairs  of  lobes. 

figures  of  several 

ut  if  the  figures  of 
)ied  by  Owen  (24, 
'k  did  not  materi- 
I,  the  structure,  or 

pes  of  brains,  the 
It  is  not  clear  to 
[)rain. 

red  (10)  the  brain 
views  of  the  optic 
3r  brains,  and  his 
I  according  to  the 
ng  olfactory  lobes 

aux  and  Vulpian 
>w.  He  makes  no 
ires  are  shown  as 
}rsal  borders,  and 
ices  distinctly  por- 
Busch. 


In  1864,  Mayer  (40)  published  figures  of  a  large  ^^f^^\f 
fisies'  brains,  as  illustrations  of  his  idea  that  by  the  relaUve  sue 
!nd  mo  e  or  less  intimate  connections  of  the  brain-lobes,  fish-hke 
jlrcTuld  be  divided  into  Pisces  Mesencephali  (Teleosts).  and 

i;^^tfiSeo:r^.i:ri.»^^ 

Th:Cnt  brain  is  represented  by  MiiUe^s  figures  ofMy.^ 
ani  BdelLoma,  and  by  an  original  and  very  ^oo^J^^^ofJe^T^^ 
^yzm  marinus.    His  interpretation  of  the  parts  differs  from  both 

^  t^ngtelXrbrains  are  copies  of  G^eus  ^r^^  Callorl.yr.^s^ 
from  Busch,  and  of  Torpedo  from  Savi ;  the  author  addmg  a  fcata 
olusTzygcem,  S^atim,  Baia  Scymnus  and  Chimera;  all 
^esro'wnfromab;ve,'c/»m«.a  alone  shows  the  olfactory  lobes ; 
Te  seplration  of  these  fVom  the  rest  of  the  brain  in  the  figure  is 
lot  reCd"  in  the  text  or  regarded  by  others  who  have  copied 

^hfbr'ain  of  Protopterus  is  seen  from  the  side  in  a  copy  of 
nw«n's  fiffure  and  ftom  above  in  that  of  Peters. 
° ZAX*.  B»«h-,  %u,e  of  the  br.io  of  I^r^  ^L 
T'  r      ^Ja  V.V  it«  Bide  elves  an  original  figure  of  that  ot  Jj. 
r«Tw^:ot  llelVuPon  the  grfat  difference  andform  and 

fl^rTs  o^  the  brains  of  Aci,enser  Hurio  and  Buthenus,  whUe  hat 
TpXln  agrees  neither  with  them  nor  with  the  preparaUons 
lJ[eC^..  There  are  copies  of  Mailer's  figure  of  the  brajn  of 
^ZrZ^s  and  of  Franque's  of  that  of  Amia.  None  of  these 
SSicate  the  existence  of  a  lateral  ventricle  or  a  foramen  of 

^The  Ganoids  together  with  the  Dipnoans  are  called  Hemiepen- 
oJhali  The  Holo-ganoidei  Include  Acipenser  and  Lepid<>steus, 
^ht  the  HemUgancJdd  embrace  Araia,  Polypterus,  Protopterus 

"^^fs^mpatbizing  with  Mayer  in  his  attempt  to  follow  out  the 
eJler  suggestion  of  Cams,  and  make  the  brain  the  basis  for  a 
b'mLX  fishes,  I  am  compelled  to  eay  that  his  detennmation 


'•**^^^'^%.;^ 


T*«.,  'y?   ,„,^,„„aMmmm4tmmilifi^ 


172 


B.      NATURAL  BISTORT. 


Of  homologiea  and  discrimination  of  groups,  as  founded  upon  the 
extfirnal  aspect  of  preparations  (some  of  which  certainly  are 
badly  preserved)  do  not  stand .  the  test  of  a  careftil  structural 
comparison.  A  smaller  number  of  figures  of  sections  or  dissec- 
tions of  a  few  typical  fonns  would  have  more  materially  aided  our 
comprehension  of  the  brains  themselves  and  of  the  zoological 
relations  of  the  flsh-like  Vertebrates. 

In  1S68  appeared  a  paper  upon  the  comparative  anatomy  and 
development  of  the  brain  by  Miklucho-Maclay  (41).  «> 

Thisauthor  regards  the  brain  of  Selachians  as  typical,  and  bases 
his  determination  of  homologies  upon  the  comparison  of  vertical 
longitudinal  sections  of  the  brains  of  an  embryo  shark  (Heptan- 
chus)  and  a  goat.  He  concludes  that  the  cerebellum  of  the  shark 
is  a  narrow  bridge ;  that  the  convoluted  mass  just  in  ftont,  which 
is  usually  regarded  as  the  cerebellum,  represents  the  optic  lobes; 
that  the  optic  lobes  are  really  the  thalami  (zwischenhim) ;  and 
that  the  hemisiAeres  (vorderhim)  are  only  partly  separated  from 
each  other. 

Remarking,  in  passing,  that  Miklucho-Maclay  offers  no  sufHcient 
reason  for  the  interpretation  of  the  hinder  lobes  of  the  brain,  I 
would  call  attention  to  the  fact  that  the  embryo  shark  was  ISO""- 
(more  than  5  inches)  in  length,  and  that,  as  shown  by  the  figure, 
the  so-called  vorderhirn  had  already  nearly  filled  up. 

His  diagram  of  a  typical  brain  (Fig.  1)  is  not  readily  or  closely 
comparable  with  any  fish-brain,  as  it  seems  to  me ;  and  since  the 
author  adopts  Muller's  statement  respecting  the  slight  extent  of 
the  ventricles  in  the  Myzonts;  and  neither  describes  nor  flgurea 
any  part  of  the  brain  of  a  Ganoid  or  Teleost,  we  are  compelled  to 
regard  his  interpretation  of  homologies  throughout  the  branch  as 
open  to  doubt,  on  account  of  the  statement  that  the  hemispheres 
of  Ganoids  and  Teleosts  are  wholly  separated  (p.  560)  ;  this  not 
being  the  case  in  any  fish-brain  excepting  that  of  Protopterua, 
where  the  true  hemispheres  are  separate  as  in  Batrachians. 

Owen  (24, 1,  figs.  178  and  174)  figures  from  above  the  brains  of 
a  sturgeon  copied  from  Busch,  and  of  Lepidosteus  apparently 
original  and  very  imperfect.  In  both,  the  masses  just  in  front  of 
the  optic  lobes  are  called  prosencephala  (hemispheres).  But,  as 
there  figured,  the  outward  aspect  of  the  two  brains  is  so  dissimilar 

t.„r  JAm"'''"  "'""  H,"'  "^^""^  '>y  ""i  «°t»  »"ebrnary,  1876.   The  del»7  in  pubUc*- 
tion  of  this  paper  eMbles  me  to  UiBert  a  comment  upon  it. 


■,«*s!*r-J 


a%t; 


if^'^'ieff^' 


B. 


HATUBAL  HISTORT. 


178 


I  founded  upon  the 
hich  certainly  are 

careftil  etructural 
sections  or  dissec- 
laterially  aided  our 

of  the  zoological 

itive  anatomy  and 
(41).  90 

I  typical,  and  bases 
parison  of  vertical 
yo  shark  {Heptan- 
ellum  of  the  shark 
ist  in  fi-ont,  which 
ts  the  optic  lobes ; 
ivischenhirn)  ;  and 
tly  separated  from 

oflTers  no  sufficient 
es  of  the  brain,  I 
•  shark  was  130""- 
own  by  the  figure, 
1  up. 

;  readily  or  closely 
le;  and  since  the 
B  slight  extent  of 
cribes  nor  figures 
!  are  compelled  to 
out  the  branch  as 
'  the  hemispheres 
p.  560)  ;  this  not 
t  of  Protopterua, 
ktrachians. 
bove  the  brains  of 
'isteus  apparently 
Bs  just  in  front  of 
pheres).    But,  as 
IS  is  so  dissimilar 

The  detoy  in  publics* 


of  Monro"  are  represented  in  the  stu^e  ^^^^^^^ 

ti„ctly,but  there  is  -^^f:^^^^T::Xl^:^..nr.^  bridge 
lum  of  the  sturgeon  is  described  as  *    «!"P'  ^y  its  down- 

orfold-accordingtoit^^outw^^^^^^^^^^^ 

ward  projection  into  the  optic  v««t"Cie  cerebellum  of 

the  cerebellum  has  a  very  "^^f^f'^"^^^^^^^  «olid,  whereas 

the  gar-pike  is  figured  as  ^^^"^'"^ ^^^  ^^^^^^^,  depressions. 
,,  U  really  Yroe^tnbTrTu)  l^S^^^     flguL  of  fishes' 
The  manual  of  Gegenoaur  y  )  aections  of  the  brains 

brains.    Three  represent  vertical  longitudi^^^^  ^ 

of  embryo  shark,  snake  "'^'i  g^'^^^^^^^;'^'  ^Pg^s  of  the  brain 
Although  the  first  --^^^^^"^^^^^^^  brain  of  a  shark 

of  Polypterua  are  copied  from  Mullei, 

X^:^.y  continent..  -^ '-•  «f  ^^'o "!"  W. 
have  no  good  English  equivalent  tor  ^^^^^^ 

rr::rr^vr;^rt:L";::-I'.-^^^^^^^^^ 

not  homogeneous;  ;j"  refrog  and  other  aerial  Vertebrates  are 
that  the  hemispheres  of  the  irog  anu  ^^^ 

optic  lote,  or  m  stark,  "J  "»  "^^  °^  „,  n,  .^k  .re  died 

.."rl'  fr^S  WorS:  .ocora.nee  with  the  pi.n  of  the 
oX''f^""' ortroptio  iobc,  respective.,  1.n.i,ph^^^ 

'  anatomlBtB. 


■■1 


■;;;:jrmiSk~imBmMSS0' 


«%iHl 


mt>mmm 


fe!,. 


B.      NATDBAL  HISTORY. 

olfactory  lobes.    But  he  does  not  refer  to  the  figure  in  the  text 
nor  does  he  mention  the  brain  as  liliely  to  aid  either  at  present  or 
in  the  future  in  the  discrimination  between  the  Ganoids  and  the 
other  fishes. 

The  figures  and  descriptions  of  the  brains  of  Myzonts  (Marsi- 
pobranchs),  Teleosts,  and  Selachians  (Elasmobranchs)  are  hardly 
more  satisfactory.  With  none  of  them  is  any  effort  made  to  ascer- 
tain,  by  a  structural  comparison,  the  extent  to  which  they  conform 
to  the  type  of  brain  commonly  recognized  among  the  air-breathing 

This  is  the  more  noteworthy  because  by  far  the  clearest  presen- 
tation of  this  type  is  f\imi8hed  by  the  figures  and  descriptions  in 
the  earlier  pages  of  the  same  work.  For  these  diagrams  indeed, 
as  for  so  many  others  which  bring  orderly  knowledge  out  of  cha- 
otic detail,  the  anatomist  is  greatly  indebted  to  Prof.  Huxley.  • 
In  this  brief  historical  survey,  considering  the  general  desire  to 
ascertain  the  extent  to  which  Ganoids  form  a  natural  group  separa- 
ble from  other  fish-like  forms,  one  is  struck  with  the  absence  of 
both  any  attempt  to  characterize  the  group  by  means  of  the  brain 
and  of  the  supposition  that  such  characterization  is  possible. 

Evidently  the  first  step  in  such  characterization  should  be  the 
identification  of  parts,  if  possible,  with  those  which  uniformly 
exist  in  the  brain  of  all  air-breathing  Vertebrates,  the  Batrachians, 
Reptiles,  Birds  and  Mammalia. 

The  ganoid  brains  upon  which  this  paper  is  based,  were  all  pre- 
pared  by  myself  fVom  fish  just  taken  from  the  water.  The  differ- 
ence  between  these  preparations  and  some  previously  made  from 
specimens  which  had  been  transported  for  some  distance  or  kept 
for  a  time  in  spirit  before  the  heads  were  opened,  has  convinced 
me  that,  for  the  determination  of  doubtful  j^oints  of  structure,  the 
brain  should  be  hardened  in  strong  alcohol  before  the  fish  has  been 
twenty-four  hours  out  of  water. 

The  published  figures  and  descriptions  of  ganoid  brains  with 
which  I  am  acquainted  appear  to  have  been  made  from  poorly 
preserved  specimens.  Moreover,  none  of  them  include  all  the 
views  (from  the  side  and  from  below  as  well  as  from  above)  and 
sections  (mesio-longitudinal,  and  transverse  at  several  points) 
which  are  necessary  to  the  presentation  of  the  rea't  «t  -jcture  of  a 
brain.  With  no  other  organ  is  it  less  safe  to  trubt  to  the  external 
form  find  appearance  of  the  several  lobes.  * 


igure  in  the  text, 
itlier  at  present  or 
Ganoids  and  the 

Mj'zonts  (Marsi- 
anchs)  are  hardly 
3rt  made  to  ascer- 
liich  they  conform 

the  air-breathing 

5  clearest  presen- 
d  descriptions  in 
diagrams  indeed, 
ledge  out  of  cha- 
rof.  Huxley.        • 
general  desire  to 
ral  group  separa- 
h  the  absence  of 
ans  of  the  brain 
is  possible, 
n  should  be  the 
which  uniformly 
the  Batrachians, 

ed,  were  all  pre- 
ter.  The  differ- 
jusly  made  from 
listance  or  kept 
[,  has  convinced 
>f  structure,  the 
ihe  fish  has  been 

Did  brains  with 
de  from  poorly 
include  all  the 
om  above)  and 
several  points) 
:  at:  "icture  of  a 
to  the  external 


B. 


KATOKAt  HMTOBT. 


176 


„„„  by  a  comparison  ot  f^ '^^'"^^^J^  „^,  with  th.  «g- 
.ke  m»i«l  -'-"""alTo  0^r^24,  1,  fig.  174),  both  ot 
Xb°'r'SKe':^°  ftom  poor,,  pre^r,^*  prep^-- 

tion8.«»  ^.  .  ^^„  .-t__  tiie  brain  here  represented, 

The  gar-pike  f-mwhvchwj«  taken  tt.e  ^^^^^  .^ 

^as  a  female,  1.3  "^^^'^^^i*?^^*,^^^^^^^^^^        so  far  as  I  know,  with 
The  brain,  as  is  usual  with  this  species        ,       ^^„„ective  tissue. 

all  adult  Ganoids,  was  covejed  ^  J  ^Aov^nmi  jet  black  and 
This  envelope  is  fatty  and  yellowi  h  m  A^^^  ^^^  ^^^  ^^^^^^  ^^^ 

very  alwndant  in  Po^oAm,  ^^Tl^  light  colored  in  A^o,  and 
the  cavity ;  moderate  in  '^'°7^^' ^^^^^^^^^^  less  than  120-  long. 
iepfdo««e«s.  In  the  young  of  t^«««  \*^^^^^^^  .^rebral  cavity.  It 
iTenvelope  exists,  the  brain  <}«  *«  ^^^;^^^^^^^^^  commences  the 
would  be  interesting  to  ascertain  at  what  pe 

j::rrrr::nr:r-'r---'''°-''' 

Tbe  ^,^^,,^tZ\->  ^  20),«Ucb,wl.bun. 

brain,  are  those  of  Huxiey  v**'    &  ,  -  34 

r;;tant  changes  are. prod^^^^^^^^^^^  ,,^„,  ^  th.ee 

According  to  Huxley  s  d««^"P  J  ^^ti^uous  with  the  central 

^     n^edian  vesicles,  w^^ose  -vUi^  -  ^^^.^^^  ..i.^ens  below  ^ 

canal  of  the  spinal  cord.    The  hm  ^^^^  ^  ^^^  ^he 

become  the  medulla  «W«nga^'*.;f  >'    '  the  anterior  part  of  this 
fourth  veruncle  (4)  ^nd  a  bridge  o^erJ^e^^  ^^^.^^^  ^^^^^^    ^^^ 

•       ventricle  is  the  '^''^^^""^  .^^^^j.  J.,  of  anthropotomy)  ;  its  cavity 
»  For  Uie  uee  of  w»eBe  bbuhw.  » 


ft 


IX-^x^ 


««a 


W-*KWi 


176 


B.     NATUBAI.  HISTORT. 


This  third  ventricle  is  the  cavity  of  the  anterior  vesicle,  and  its 
lateral  walls  become  the  thalami  {Th).  But  from  each  side  in 
fVont  there  is  produced  a  hollow  bud  which  enlarges  so  as  to  be- 
come the  cerebral  hemisphere  (H).  From  the  front  of  each  hemis- 
phere a  second  bud  is  produced,  the  olfactory  lobe  {01).  The 
cnvity  of  each  hemisphere  is  a  lateral  (first  or  second)  ventricle, 
(LV)  and  the  cavity  of  the  olfactory  lobe  is  the  olfactory  ventricle. 
The  constricted  communication  between  each  lateral  ventricle  and 
the  median  third  ventricle  is  known  as  the  ^^ foramen  of  Monro  " 
(FM).  Median  dorsal  and  ventral  outgrowths  from  the  thalamus 
vesicle  become  respectively  conarium  ("pineal  body,"  Co)  and 
infundibulum,  the  connection  of  which  with  the  hypophyAi  (Hy) 
is  now  regarded  as  secondary  (43,  92). 

The  thin  anterior  wall  of  the  anterior  vesicle  between  the  hemis- 
phere-buds, remains  as  the  lamina  terminalia  (Lt)  the  "lamina 
cinerea"  of  anthropotomy.  The  corpus  striatum  is  a  thickening 
of  the  outer  walls  of  the  hemisphere  {CS).  The  various  trans- 
verse and  longitudinal  commissures  corpus  callosum,  anterior  com' 
missure,  fornix  and  pons  Varolii,  probably  do  not  exist  in  fishes 
and  need  not  here  be  described. 

Taking  for  granted  the  sequence  of  principal  ganglia,  medulla, 
cerebellum,  optic  lobes,  thalami,  hemispheres  and  olfactory  lobes, 
no  difficulty  is  met  in  recognizing  the  three  first  named  in  the 
brain  of  Lepidosteua,  But  the  appearance  of  these  in  the  section 
differs  considerably  from  the  idea  conveyed  by  the  figures  of  the 
brain  fi-om  above  and  below.  The  fourth  ventricle  (IV)  extends 
farther  back,  and  has  no  bridge  across  its  anterior  end  as  in 
Huxley's  figure.  In  this  species  the  hinder  end  is  quite  sharply 
pointed.  But  in  a  smaller  gar  ft-om  Wisconsin,  not  yet  identified, 
the  ventricle  is  shorter,  its  borders  are  raised  and  everted,  and  the 
hinder  extremity  less  sharp.  The  borders  also  approach  each 
other  quite  nearly,  just  behind  the  cerebellum,  which,  with  a  poorly 
preserved  preparation,  might  lead  an  artist,  not  an  anatomist,  to 
regard  them  as  normally  continuous.^ 

If  figure  7  be  held  with  the  olfactory  lobe  upward,  then  the  sec- 
tion of  the  entire  cerebellum  may  be  compared  to  a  letter  S,  the 
lower  curve  larger  and  its  substance  thicker  than  the  upper. 

The  lower,  or,  if  the  figure  be  replaced  in  the  horizontal  posi- 

x>  Huxley's  Sgan  purports  to  be  of  the  brain  of  L,  temiratHatu$,  Ag,  QUnther  re- 
garda  thii  as  a  synonym  of  L.  o$$eu». 


•  ,*- 


^..   .  -S* 


'*-lro 


B. 


NATUBAt  HISTOBt. 


r  vesicle,  and  its 
'om  each  side  in 
I'ges  so  as  to  be« 
it  of  each  hemis- 
lobe  (01).  The 
second)  ventricle, 
Ifactory  ventricle. 
ral  ventricle  and 
xmen  of  Monro  " 
om  the  thalamus 
)ody,"  Co)  and 
lypophyUlB  (Hy) 

wesn  the  hemis^ 
jt)  the  "lamina 
is  a  thickening 
3  various  trans- 
»i,  anterior  com' 
i  exist  in  fishes 

inglia,  medulla, 
olfactory  lobes, 
'  named  in  the 
3  in  the  section 
i  figures  of  the 
e  (IV)  extends 
rior  end  as  in 
B  quite  sharply 
;  yet  identified, 
rerted,  and  the 
approach  each 
,  with  a  poorly 
I  anatomist,  to 

I,  then  the  sec- 
a  letter  S,  the 
3  upper. 
>rizontaI  post- 

>,Ag.   GUntherrO' 


«on,  posterior  curve,  '^P;:^ t^  ^W^T  ^r.'"" 

anterior   curve    ^^^^^^P^^  .f^^jrof  Gottsche"  referred  to  by 
antbropotomy,  and  to  the     fornix  ^^.^^ 

Huxley  in  his  descnpt.on  "fj^/ ^jf  "^,^,^„e«3  of  the  cerebellum 
This  part  is  about  one-half  J^e  'Wck  ^^ 

Hself,  an'd  it  becomes  an  -«-'  "«  \^J",^:;:  lobes.    The  cere- 
the  overhanging  postenor  bo  dcr  J^  *^    J  ^elng  more 

About  midway  '^f-Z^neST^ --^^^^^"^  portion  upon 
cerebellum  and  the  free  thin  edge  or^  .^  .^  apposition 

the  ventral  aspect,  Is  a  low  ndge.    ^^^^'^ J,„^^,. 
with  a  correspond  ng  ever  ed  edge  o    t^^  ^^  ^^^^  ^.,,  , 

The  dorsal  surface  of  ^J«  f  ^f  ^"J^,^  mounded  portion  f^om 
rather  deep  ftirrow  separating  the  meai 
the  peduncle  on  e«^^J»  «;d;:        .^g^  ^,  ^  rather  contracted  passage 

The  "  aqueduct  of  Sylvius  J^-^*^'  .  ,.     ^ptic  lobes. 

ftom  the^ourth  ventricle  J^J^;— ^L^^^^^^  downward  and 

The  dorsal  aspect  of  the  optic  ;3        ..^  ^i^e  cerebellum  m- 

forward  at  about  the  ^'^-^'^ 'fl^^tTlrfac.  Is  about  the 

cimes  back^rd.    The  t^^^^^^^/Jf  °[  j^^  .?;„t  the  anterior  margin 

same  as  that  of  the  "  fornix  of  Gottsche,   but  ^^^  ^ 

ts  slightly  thickened  and  rounded^  ^^^^^J^^acted  aperture  sur- 

°P*^°Tr^\^a^-2r'S^e  cllmor  pineal  body  (O  lies 
rounded  by  a  flarmg  up- 

just  In  front  of  this  aperture.  doubting  the  correct- 

^    So  far  there  seems  no  reasonable  cause  fo^^^^    But  the  anterior 

half  of  the  brain  of  ^»<^^««'  ^^^^r^^,  of  the  higher  Verte- 

the  way  of  strict  comparison  with  the 

brates.3«  ^^^  2,  3,  4,  cannot 

'•'•rrw         B.  (1«J 


.  A.  A.  B.  VOL.  xxrr.    a. 


f  ■ 


'^ 


v 


178 


B.      NATURAL  HISTORT. 


tends  under  nearly  the  whole  width  of  the  brain  and  opens  down- 
ward  hy  a  median  silt  into  what  seems  to  be  a  plexus  of  vessels. 

The  hollow  lateral  lobes  are  what  Owen  calls  "hypoaria"  and 
Huxley,  with  most  authors,  "  lobi  infcriores."  The  lower  solid  vas- 
cular mass  corresponds  to  what  is  commonly  called  the  pituitary 
body  or  hypophysis.  It  is  easily  detached,  and  is  not,  so  far  as  I 
am  aware,  represented  in  any  figure  of  a  Ganoid  brain. 

Pending  an  examination  of  the  brain  of  Lophiua,  the  hypophy- 
sis of  which  lies  far  in  front  of  the  brain  connected  with  its  usual 
attachment  by  a  very  long  inftindibulum,  I  am  inclined  to  regard 
the  lobi  infcriores  as  lateral  expansions"''  of  what  is  called  in 
anthropotomy  the  tuber  cinereum. 

There  remain  to  be  described  the  two  pair  of  m.i^ses  which,  in 
Lepidoateus  as  in  most  Teleosts,  are  placed  jus*  iii  front  of  the 
optic  lobes.  They  are  at  the  present  time  usually  regarded  as 
representing  respectively  the  hemispheres  and  olfactory  lobes. 

According  to  the  type  of  brain  as  described  by  Huxley  and 
generally  accepted,  the  hemispheres  should  be  lateral  masses 
separate  from  each  other  and  each  containing  a  cavity,  the  lateral 
ventricle,  communicating  with  the  median  or  third  ventricle  through 
a  foramen  of  Monro. 

Yet,  so  far  aa  I  am,  avoare,  no  mci,  condition  of  things  haa  been 
figured  or  described  with  respect  to  the  brain  of  any  fish-like  form 
excepting  Protopterua  and  Lepidosiren.^    (See  Appendix.) 

In  the  brain  of  the  adult  Lepidoateua,  the  lateral  mass  marked 
PTh  Is  a  solid  lamina  with  its  upper  or  dorsal  border  everted,  as 
seen  in  the  transverse  section  (Fig.  11).  The  mesial  surface  of 
its  rounded  dorsal  aspect  presents  two  fkirrows.  It  is  Joined  with 
its  fellow  of  the  opposite  side  by  a  large  commissure  (B)»  and  by 
a  thinner  lamina  reaching  back  to  the  optic  chlasma. 

"  Dr.  Cleland  (88, 203)  regards  the  hypoaria  of  osseoas  dshet  aa  the  thalami,  and 
states  that "  in  variuiis  flgheH,  the  optic  nerves  arise  from  them  as  well  as  from  the  optio 
lobes."  Dr.  Cleland's  learning  and  accuracy  are  such  that  I  would  not  reject  his  view 
upon  less  grounds  than  those  here  presented.  But  I  have  not  obterred  the  origin  of 
the  optic  nerves  from  the  hypoaria  in  any  llsb. 

«•  Tiedemann  frankly  admits  (35, 864),  that  "we  find  no  trace  of  lateral  ventricles  In 
the  osseous  Bshes;"  he  regarding  the  so-called  hemispheres  as  ttie  corpora  striMta  (p. 
«80).  Contrast  this  with  the  loose  statement  of  Vulpian  (SI,  821),  "  on  tronve  parfols 
des  rudiments  de  ventricules  Interaux  dans  les  lobes  c^r^braux"  of  osseous  fishes. 

The  so-called  ventricles  of  Selachians  will  be  shown  heraafter  to  be  remnanU  of  th« 
third  ventricle;  not  rudiments  of  the  first  and  second. 

*•  This  is  apparently  what  Oottsche  called  In  osseous  fishes, "  commiiiura  Interlob- 
nlarla." 


tJVS- 


^*-    •*•  >    ^.  ■«wr»^«c -.-"^  •fc»»,-»  • 


•   I 


■   tr-, 


B.      NATURAL  tllSTORT. 


179 


land  opens  down- 
|loxu8  of  vessels. 
"bypoaria"and 
!  lower  solid  vas- 
|ed  the  pituitary 
I"  not,  so  far  as  I 
■brain. 

us,  the  hypophy. 
etl  with  its  usual 
dined  to  regard 
hat  is  called  in 

i.idseg  which,  in 
««  front  of  the 

»ny  regarded  as 

ictory  lobes. 

by  Huxley  and 
lateral  masses 

'vity,  the  lateral 

k'entricle  through 


'  things  has  been 
»y  Jish-like  form 
pendix.) 
al  mass  marked 
rder  everted,  as 
aesial  surface  of 
t  is  Joined  with 
•e  {B)«  and  by 


w  »he  thalami,  and 

iIIasA-omttieoptio 
not  reject  hU  view 
erred  the  origin  of 

uteral  ventrlclei  in 
corpora  ttriMta  (p. 
on  troure  parfoia 
oaseoua  flsiiea. 
•  remnanu  of  th« 

imUaura  intertob- 


Just  in  front  of  each  of  these  lobes  is  a  rounded  orifice  opening 
obliquely  outward  and  forward  into  the  base  of  the  anterior  or 
olfactory  lobes. 

This  orifice  is  wholly  invisible  from  above  or  below  or  from  the 
outer  side,  and,  although  figured  by  Stannius  in  the  sturgeon, 
seems  to  have  attracted  no  attention  from  those  who  have  studied 
Ganoid  brains. 

It  leadfl  into  a  cavity  which  extends  the  whole  length  of  the  so- 
called  olfactory  lobe,  and  is  about  1"""-  In  diameter. 

As  this  is  the  only  lateral  opening  from  the  median  ventricle 
there  seems  to  be  no  escape  from  the  conclusion  that  it  is  the 
*'  foramen  of  Mw<nro,"  and  that  the  cavity  into  which  it  leads  is, 
wholly  or  in  part,  the  lateral  ventricle. 

Where  then  are  the  hemispheres? 

The  mesial  border  of  the  foramen  of  Monro  is  slightly  raised, 
so  as  to  be  distinguishable  upon  close  inspection  from  the  olfac- 
tory lobe.  Still  it  is  very  small,  and  upon  a  poorly  preserved 
specimen,  or  under  a  brief  examination  it  might  escape  notice 
altogether. 

But  if  the  corresponding  parts  of  other  Ganoid  brains  be  care- 
Ailly  examined,  they  will  be  seen  to  present  the  same  foramen, 
while  in  all  of  therj  the  anterior  Up  is  decidedly  broader,  present- 
ing the  appearance  of  a  separate  lobe.     See  figures  8,  9,  10. 

Shall  we  conclude  that  the  hemispherb  and  olfactory  lobe  are 
undifferentiated,  or  regard  the  lip  already  described  as  a  rudimen- 
tary hemisphere.  This  latter  is  the  conclusion  to  which  I  am 
inclined. 

It  involves,  as  a  corollary,  the  interpretation  of  the  lateral 
masses  between  the  optic  lobes  and  those  Just  described,  as  repre- 
senting the  whole  or  some  part  of  the  thcUami,  or  lobi  verUricuii 
tertii. 

In  Lepidosteus  one  would  be  inclined  to  regard  the  lateral 
masses  as  the  whole  thalamus.  But  in  Amia  the  distance  between 
the  front  of  the  optic  lobes  and  the  hinder  surface  of  these  masses 
equals  that  of  the  masses  themselves.  In  Polypterua  likewise,  as 
figured  by  Miiller,  it  is  considerable.  In  Chimera  what  seems  to 
be  a  corresponding  region  is  very  much  elongated.  In  most 
Selachian  brains  it  is  quite  extensive. 

For  the  sake  of  distinction  therefore,  we  may  call  the  anterior 
lateral  masses  protftalami^  and  the  portion  connecting  them  with 


\^ 


I 


.v_.Wi«Sli 


180 


B.      NATUBAL   HISTORY. 


f:        ^1 


k- 


\ 


tho  brain  behind  the  cmra  thalami.  These  latter  nocm  to  corres- 
pond to  tlie  thalami  of  the  higher  Vertebrates ;  tho  third  ventricle 
lies  between  them,  the  conarium  above  and  the  hypophysis  below. 

Aside  fVom  the  adverse  opinions  of  all  authors  (which,  however, 
are  of  less  importance  in  view  of  the  imperfection  of  tlio  material 
at  their  disposal)  the  only  objection  to  this  view  is,  that  it  makes 
the  hemispheres  so  much  smaller  than  cither  the  thalami  or  the 
olfactory  lobes. 

It  is  to  be  remembered,  however,  that  mere  size  is  of  no  value 
for  tho  determination  of  homologies.  The  cerebellum  is  recognized 
as  such  in  the  lamprey  and  the  salamander  because  it  is  a  bridge 
over  the  fourth  ventricle,  although  it  is  "o  much  smaller  than  the 
corresponding  organ  of  the  bird  oi'  mammal. 

The  hemispheres  are  hardly  larger  than  the  optic  lobes  in  some 
Batrachians,  while  in  man  they  overshadow  all  the  other  parts. 

Now  the  hemispheres  are,  by  development,  mere  buds  fk-om  the 
thalami,  yet,  as  may  happen  with  human  families,  the  offspring 
are  larger  than  the  parents.  In  like  manner,  in  the  Ganoid  brain, 
the  hemispheres  themselves  are  surpassed  in  size  by  their  buds^ 
the  olfactory  lobes.         ,.t      .., 

But  while  regarding  the  view  here  advanced  as  based  upon 
sound  morphological  grounds,  the  large  size  and  convoluted  surface 
of  the  thalami  suggests  the  idea  that  they  may  in  some  way  /unc- 
tionally  represent  the  hemispheres. 

For  the  determination  of  this  the  brain  should  be  examined 
microscopically  and  the  fibres  from  the  medulla  should  be  traced 
forward  into  the  several  lobes  as  has  been  done  with  the  ftog  by 
Wyman  and  Stieda.  They  should  also  be  experimented  upon  by 
injury,  ablation  and  galvanic  stimulation. 

To  complete  the  evidence  we  should  find,  at  least  in  young  spec- 
imens, something  like  a  lamina  terminalis,  connecting  the  rudimen- 
tary hemispheres  just  in  fVont  of  the  foramina  of  Monro.  No  such 
has  been  found  by  me  in  Amia  or  Lepidoatena,  but  the  sturgeon 
and  Polyodon  present  a  transverse  curtain  with  foldings  upon  the 
deep  surface  resembling  those  of  the  curtain  over  the  fourth  vent- 
ricle of  Batrachians  and  lamprey-eels.  Though  not,  apparently,  of 
nervous  tissue,  it  may  nevertheless,  represent  the  lamina  terminalis. 
For  there  is  reason  to  believe  that,  in  the  course  of  development, 
many  parts  of  the  roof  of  the  primary  vesicles  may  become  merely 
connective  and  vascular  tissue.  . 


>*    *■»»■»     ■  •   ^    J',    ia> f*,->» 


'v 


B.      NATURAL  niSTORT. 


181 


"  8Gcm  to  corres- 
ho  third  ventiiclo 
fPophysis  below. 
|; which,  however, 

of  the  material 
■».  thut  it  makes 

thalami  or  the 

|o  is  of  no  value 
jum  is  recognized 
he  it  is  a  bridge 
pmaller  than  the 

lie  lobes  in  some 

other  parts. 
e  buds  ft-om  the 
'8,  the  offspring 
>e  Ganoid  brain, 

by  their  buds, 

as  based  upon 

nvoluted  surface 

some  way/uno- 

d  be  examined 
Jould  be  traced 
I'ith  the  ft-og  by 
lented  upon  by 

in  young  spec- 
'g  the  rudimen- 
•nro.    No  such 
t  the  sturgeon 
lings  upon  the 
ie  fourth  vent- 
apparently,  of 
ina  terminalis. 
development, 
ccome  merely 


In  a  young  Lepidosteus  151"""'  long,  the  dorsal  borders  of  tlie 
prothalnini  re  not  everted  as  in  the  adult.  For  reasons  wliich 
will  be  undorstood  when  the  brains  of  Selachians  and  Myzonts  are 
desoril>cd,  I  am  inclined  to  think  that  at  an  earlier  period  of  devel- 
opment the  dorsal  bonlers  were  united. 

Detailed  descriptions  of  the  brains  of  the  other  Ganoids  are  de- 
fcrrcd  until  figures  can  be  presented.  That  of  Aviia  closely  rc- 
BcmbluB  that  of  LepidoHteua,  especially  in  the  cerebellum.  The 
infundibulum  is  more  folded.  The  crura  thalumi  are  considerably 
longer. 

The  brain  of  Acipenaer^°  and  Polyodon  are  very  similar  in  both 
structure  und  general  appearance.  In  both  the  cerebellum  is 
apparently  a  narrow  bridge,  but,  as  seen  in  the  figure  of  Stannius, 
it  really  extends  far  forward  into  the  optic  ventricle,  as  an  exag- 
gerated fornix  of  Gottschc.  The  walls  of  the  optic  lobes  are 
thicker  In  Polyodon  than  in  Acipeneer,  The  brain  of  Scaphyrhyn- 
chua  was  not  obtained  for  examination.  There  if  no  reason  for 
supposing  it  to  differ  essentially  from  that  of  Acipenaer. 

MiJller's  figures  and  descriptions  of  the  brain  of  Polypterua  do 
not  allude  to  the  communication  between  the  median  ventricle  and 
the  olfactory  ventricles,  but  the  figures  are  quite  insuflScient,  and 
pending  its  examination  with  reference  to  this  point,  we  may  infer 
that  it  agrees  with  Lepidoateua  in  this  respect  as  in  the  eversion  of 
the  thalami.  .  .  , 

The  brain  oft  amoichthys  is  not  known  to  me.  We  may  even 
more  naturally  infer  its  agreement  with  that  of  Polypterua. 

Provisionally,  at  least,  the  seven  genera,  Amia  and  Lepidoateua^ 
Polypterus  nnd  Calamoichthya,  Acipenaer ,  Scaphyrhynchua  and  Pol- 
yodon, maN  l)e  associated  as  having  rudimentary  hemiapherea  in  the 
form  of  nl'jhtly  raised  bordera  of  the  foramina  of  Monro  and  much 
smaller  than  the  olfactory  lobea;  large  prothaXami  connected  below 
by  a  commiaaure  but  having  their  doraal  bordera  free  and  more  or 
leaa  everted;  an  optic  chiasma;  a  rythmically  contractile  and  multi- 
valvular  bulbua  arteriosus. 

Fig.  12  shows  a  mesial  section  of  what  seems  to  me  to  be  a 
typical  Ganoid  brain  with  cross  sections  at  characteristic  points. 

Let  us  now  see  whether  the  above  definition  includes  any  other 
Vertebrates. 


»>  Three  species  of  this  genus  were  examined,  rubkundue,  oxyrhynehu$,  and 
t  nndetermlnod. 


oneM 


yet  undetermlnocl. 


-^.s^i^mmMr 


T^.'i^i^l'** 


182 


B.      NATURAL  HISTOBT. 


Amphioxus  appears  to  have  only  a  medulla  with  a  fourth  ventri- 
cle. The  part  in  ft'ont  of  the  ventricle  may  be  regarded  as  an  un- 
differentiated representative  of  the  brain  of  the  higher  Vertebrates 
(Langerhans  (44,  297)  says  he  finds  a  small  olfactory  lobe). 

In  Myxine  and  Bdellostomd,  Joh.  Miiller  (37),  found  no  ventri- 
cle in  front  of  the  fourth,  and  no  cerebellum.  In  a  somewhat  in- 
jured preparation  of  the  brain  of  Myxine,  I  find  what  seems  to  be 
a  thin  and  rudimentairy  cerebellum  ;  and  a  median  ventricle  which 
extends  forward  to  the  base  of  the  anterior  pair  of  lobes,  which 
Miiller  and  all  other  authors  regard  as  the  olfactory  lobes.  On 
each  side  at  this  point  is  a  slit-like  orifice  leading  into  the  cavity 
of  the  olfactory  lobe.  These  can  be  no  other  than  the  foramina 
of  Monro  and  lateral  ventricles.  The  liemi spheres  are  hardly  dis- 
tinguishable from  the  olfactory  lobes.  The  larger  pair  of  lobes 
just  behind,  since  they  form  the  walls  of  a  median  ventricle  must 
be  regarded  as  the  undifferentiated  prothalami  and  thalamr.  They 
differ  from  thoib  of  Ganoids  in  being  connected  above  as  well  as 
below.  But  behind  them  are  the  conarium  and  the  orifice  of  the 
optic  ventricle  just  as  in  the  brain  of  Lepidosteus.  In  Petromyzon 
Miiller  found  (87)  the  third  ventricle  only.  In  several  well  pre- 
served preparations  of  the  brain  of  the  large  sea-lamprey  (P. 
marinus,  var.  Americanus),  I  find  at  the  anterior  extremity  of  this 
median  cavity,  as  in  Myxine,  a  foramen  of  Monro  leading  intO'  the 
olfactory  or  lateral  ventricle.  The  thalami  are  closed  above  as  in 
Myxine.  The  distinct  lobes  which  project  just  behind  the  olfac- 
tory lobes  are  probably  hemispheres.     (See  Appendix.) 

Miiller  describes  the  optic  nerves  of  the  Myzonts  as  not  crossing 
at  all.  Upon  this  ground,  aa  by  the  non-separation  of  the  thalami 
above  and  the  lack  of  several  rows  of  valves  in  the  bulbus  arte- 
riosus, they  differ  from  the  Ganoids.  In  figure  13  {M)  i»  repre- 
sented a  cross  section  of  the  brain  of  Petromyzon  through  the 
thalami.     (See  Appendix.) 

The  Selachians  (here  restricting  the  term  to  the  sharks  and 
skates)  have  a  brain  which  is  really  only  a  complex  modification 
of  the  Lamprey's.  In  an  embryo  shark  {Mustelus  eanis)  37""°- 
(about  IJ  inches)  i«  length,  that  part  which  gives  rise  to  the 
olfactory  crura  and  which  has  been  variously  interpreted  as  hemis- 
pheres alone,  hemispheres  and  thalami,  and  thickened  lamina  ter- 
minalis,  is  a  large  vesicle  with  thin  walls  and  a  single  cavity. 
This  communicates  behind  with  the  optic  ventricle  and  om  each 


aMif.««»»^4 


")r^ 


ith  a  fourth  ventri- 
regarded  as  an  un- 
higher  Vertebrates 
ractory  lobe). 
[)»  found  no  ventri- 
In  a  somewhat  in- 
what  seems  to  be 
an  ventricle  which 
tir  of  lobes,  which 
factory  lobes.    On 
ng  into  the  cavity 
than  the  foramina 
>res  are  hardly  dis- 
kger  pair  of  "lobes 
'ian  ventricle  must 
fl  thalami.    They 
above  as  well  as 
the  orifice  of  the 
3'    In  Petromyzon 
J  several  well  pre- 
p  sea-lamprey  (p. 
r  extremity  of  this 
ro  leading  into,  the 
5losed  above  as  in 
behind  the  olfac- 
endix.) 

its  as  not  crossing 
an  of  the  thalami 
the  bulbus  arte- 
13  {M)  is  repre- 
«o»  through  the 

the  sharks  and 
lex  njodification 
lu8  eanis)  37'»"n- 
ves  rise  to  the 
►reted  as  hemis- 
aed  lamina  ter- 

single  cavity, 
e  and  on  each 


B.      NATURAL  HISTORY. 


183 


side  in  firont  with  the  cavity  of  a  little  bud  which  is  in  contact  with 
the  nasal  sack.  The  vesicle  is  evidently  the  expanded  prothalamus 
closed  above  as  in  the  Myzonts.  In  the  adult  Selachians  (as  I 
hope  to  show  by  a  series  of  figures  at  a  future  time)  we  must 
suppose  the  original  median  cavity  to  have  gradually  filled  up  so 
as  to  leave  only  two  slender  passages,  near  the  lower  wall,  which 
start  fVom  opposite  the  optic  foramen  behind,  and  diverge  to  enter 
the  olfactory  ventricles  in  front.  The  degree  of  differentiation  of 
the  crura  thalami,  and  the  hemispheres,  will  be  more  fully  described 
hereafter.  In  some  forms  the  hemispheres  are  distinctly  con- 
stricted from  the  sides  of  the  nearly  solid  prothalamus.  Although, 
therefore,  the  optic  chiasma  and  multivalvular  and  contractile  bul- 
bus and  some  other  characters  are  common  to  Ganoids  and  Sela- 
chians, the  prothalamus  is  open  in  the  former  and  closed  in  the 
latter.  In  these  and  some  other  respects  the  contrast  between 
the  two  groups  is  noteworthy.  In  figure  13,  ES  represents  a 
cross  section  of  the  prothalamus  of  an  embryo  shark  and  AS  that 
of  an  adult. 

The  Holocephali  (Chimera  and  Callorhynchus)  are  commonly 
arranged  with  or  near  the  Selachians.  They  have  many  features 
in  common  and  the  intromittent  organs  upon  the  ventral  fins  are 
usually  regarded  as  very  important.  Being  a  purely  sexual  appa- 
ratus we  may  question  whether  their  taxonomic  value  is  equal  to 
that  of  the  brain.  Not  having  had  the  opportunity  of  examining 
a  brain  31  I  can  only  judge  from  the  figure  by  Busch,  copied  by 

»Ju8t  as  this  goes  to  press  I  am  enalJIed,  through  the  kindness  of  Mr.  Alex.  Agassis, 
to  expose  and  examine  the  brain  of  a  well-preserved  male  Chimera  in  the  Museum  of 
Comparative  Zoology.  The  oerebellnm  is  very  large  and  covers  the  optic  lobes;  but  is 
not  folded  transversely  as  in  most,  if  not  aU,  adult  sharks  and  skates.  The  crura 
thalami  are  very  long  and  thin  and  united  ventrally  by  a  delicate  membrane  apparently 
only  pia  mater.  Anteriorly  each  cms  expands  Into  a  prothalamus,  the  dorsal  border 
of  which  is  thin  and  slightly  everted.  This  prothalamus,  however,  instead  of  forming 
the  principal  anterior  mass  as  in  Qsnoids,  Is  overlapped  outside  by  a  large  and  elon- 
gated hemisphere  abouPS°"»'  in  height  and  16'»-  in  length.  On  the  hinder  third  of  the 
mesial  surface  is  a  large  rounded  foramen  of  Monro,  4f^  in  diameter.  The  lateral 
ventricle  extends  forward  into  the  olfiictory  lobe.  Into  the  fttramen,  and  occupying  its 
entire  area,  projects  a  thickening  of  the  outer  wall  of  the  hemisphere  which  may  rep- 
resent a  primordial  corpus  striatum.  Just  in  ftt>nt  of  the  foramen  the  ventral  borders 
of  the  hemispheres  are  connected  by  a  transverse  oommissuro.  I  greatly  regret  not 
having  been  able  to  examine  this  brain  before  presenting  this  paper.  It  seems  to  flir- 
nish  an  actnal  form  intermediate  between  the  apparenUy  distinct  types  represented  by 
the  brains  of  Selachians,  Ganoids  and  Dipnoans.  If  I  correctly  interpret  the  appear- 
ance of  a  partial  subdivision  of  the  elongated  mass  behind  the  olfactory  lobe  the  Chi- 
mera's brain  presents  a  more  equal  proportion  of  hemisphere  and  prothalamus  than 
exists  in  Ganoids  or  Teleosts,  where  the  former  seems  to  be  reduced  to  a  rudiment 
hardly  recognizable  as  such. 


-^^^ 


^nf^mi.  II  (W'^-'sw^ 


I 


f 


•fAAsurjj  \-»f^..~. 


I. 


184 


B.      NATURAL  HISTORY. 


Owen  (24,  fig.  179).  The  cerebellum  appears  like  that  of  the 
sharks  and  skates.  But  the  elongated  crura  thalami,  and  what 
seem  to  be  somewhat  expanded  prothalami,  and  the  rudimentary 
hemispheres,  indicate  a  close  similarity  with  the  Ganoid  type. 
The  brain  should  be  carefully  reexamined,  and  that  of  a  very 
young  embryo  would  be  especially  valuable. 

The  figure  of  the  brain  of  Protopterus  (Owen,  25  and  24)  might 
be  taken  for  that  of  Menopoma  or  Menobrmchus.  It  has  no  appar- 
ent resemblance  to  either  the  Ganoid  or  the  Selachian  type.  There 
are  also  true  nostrils,  and,  according  to  Huxley  (7,  147),  a  small 
pulmonary  auricle.  These  characters  united  with  those  of  the 
brain  seem  to  offer  strong  grounds  against  the  association  of  the 
Dipnoi  with  the  Ganoids,  excepting  as  a  very  generalized  type 
combining  Ganoid  and  Batrachian  features.  'The  brain  of  Cera- 
todua  has  not  been  described.^* 

Of  fish-like  forms  there  remain  the  Teleostei.  They  may  at 
once  be  distinguished  from  all  others  by  the  non-rythmically  con- 
tractile  bulbus  provided  with  a  single  row  of  valves  and  by  the 
decussation  of  the  optic  nerves  without  a  chiasma.^s 

A  sufficient  number  of  Teleost  brains  has  not  yet  been  care- 
fully examined  to  enable  us  to  generalize  with  safety.  But  so  far' 
as  they  are  known  we  may  characterize  them  as  having  solid  lateral 
masses  (prothalami),  their  dorsal  borders  separate  and  sometimes 
everted,  and  with  the  olfactory  lobes  sometimes  in  contact  with 
the  prothalami,  sometimes  in  contact  with  the  olfactory  sacks  and 
connected  with  the  prothalami  by  more  or  less  elongated  crura. 

Since  this  paper  was  presented  t  have  found  small  foramina 
of  Monro  and  ventricles  in  Perm  flavescens,  Anguilla  Bostoni- 
ensis  and  Scomber  vemalia.    They,  however,  are  much  smaller 

"In  "Natare"  for  Jan.  6th,  1876,  It  i.  .tated  that  Prof.  Hnxley  described,  for  the 
flrst  time,  the  brain  of  Ceratodut  at  the  meeting  of  Uie  Zoological  Society,  Jan.  4th :  that 
he  showed  how  closely  It  resembled  that  of  Lepidoiiren,  and  that  in  some  points  it 
resembled  th«  Selachian  rather  than  the  Ganoid  type.  He  laid  especial  stress  upon  the 
affinities  of  the  animal  with  CAfmera. 

Zoaioglsts  win  look  with  great  interest  for  this  paper  on  acoonnt  of  the  descriptloa 
and  flgiires  of  the  brain  of  a  form  which  has  aroused  so  much  discnssion,  and  also  for 
the  morphological  and  tazonomic  considerations  which  can  hardly  faU  to  throw  irreat 
light  upon  the  relations  of  the  flsh-like  Vei  tebrates. 

"  Gottsche  (30,  476,  aad  flg.  xxxiii),  refers  to  a  remarkable  rariation  of  the  optio 
nerves  described  by  Weber  (Meckel's  Archly.  1873,  p.  317).  In  an  example  of  Clupea 
ftar«Hj«.  t)-,  ncrre  of  the  left  eye  was  pierced  by  that  of  the  right.  The  ttructure  of 
the  chiasma  of  Ganoids  and  Selachians  should  be  oareitally  examined  to  ascertain  how 
completely  the  libers  cross,  or  intermingle,  or  connect  the  eyes  and  lobes  of  the  two 
Bides  together. 


.7  v-s-^--    . 


<e  that  of  the 

ami,  and  what 

Pe  rudimentary 

I  Ganoid   type. 

Ihat  of  a  very 

[and  24)  might 
has  no  appar- 
'type.    There 
■»  147),  a  small 
those  of  the 
kiation  of  the 
peralized  type 
orain  of  Cera- 

They  may  at 
[thmically  con- 
!8  and  by  the 

'et  been  care- 
•    But  so  far' 

g  solid  lateral 

^d  sometimes 
contact  with 

>ry  sacks  and 

ted  crura. 

•all  foramina 

nlla  BoatonU 

luch  smaller 

iscribed,  for  tba 
iy.  Jan.  «h;  that 
some  points  it 
stresB  upon  tlie 

the  descriptioB 

•n,  and  also  for  ' 

So  tbrow  great 

»  of  the  optio 
»Ple  of  Clupta 
"o  structure  of 
••nertain  liow 
e«  of  tlie  two 


B.      NATURAL  BISTORT. 


185 


than  in  Ganoids,  and  I  give  a  provisional  figure  (Fig.  14)  mainly 
for  the  purpose  of  calling  attention  to  the  point  where  they  are  to 
be  looked  for.  Probably  they  are  proportionally  larger  in  embryo 
brains.  They  may  become  wholly  obliterated  in  some  adults,  es- 
pecially those  with  olfactory  crura.  They  should  be  looked  for 
in  large  species,  as  Esox^  Xiphias,  Hippogloama,  etc.,  where  the 
olfactory  lobes  are  sessile.^^ 

The  following  table  exhibits  the  above  mentioned  charaet^s  in 
a  more  condensed  form.  But  it  must  not  be  inferred  that  the 
order  of  names  indicates  my  belief  respecting  either  their  rank, 
their  aflQnities,  or  geological  succession.  In  the  first  place  no 
linear  arrangement  can  do  this.  In  the  second,  while  the  Teleosts 
seem  to  most  perfectly  and  abundantly  embody  the  Jish  idea  and 
their  geological  relations  and  the  structure  of  some  parts  would 
lead  us  to  place  them  highest  in  the  fish  series,  yet  the  non-ming- 
ling of  the  optic  nerves  and  the  very  embryonic  condition  of  the 
kidneys  as  compared  with  those  of  Selachians,^^  seem  to  place  them 
next  the  Myzonts. 

The  air-breathing  Vertebrates  are  added  in  order  to  complete 
the  series. 

Provisional  Arranoehent  of  Vertebrates  according  to  Cere- 
bral AMD  Cardiac  Characters. 

Leptocardii.  (Amphioxus).  Brain  not  differentiated  from 
medulla.    Heart  a  contractile  tube. 

Mtzonts.  (Maroipobranchii).  Optic  nerves  do  not  cross 
(Miiller).  Single  median  nostril.  Hemispheres  smaller  than  ol- 
factory lobes.  Thalamus  and  prothalamus  not  distinctly  sepa- 
rated. Thalamus  closed  forward  and  dorsad.  Cerebellum  a 
narrow  and  thin  lamina;  perhaps  wanting  in  Myrinolds.  (See 
Appendix.) 

Selachians.  (Elasmobranchii.)  Optic  chiasma.  Rhythmically 
contractile  bulbus  arteriosus,  with  several  rows  of  valves.  Olfac- 
tory lobes  '  pedunculated.  Hemispheres  smaller  than  olfactory 
lobes.    Prothalami  and  thalaml  distinct ;  the  latter  as  crura.     In 

**  The  brains  mast  be  well  preserved. 
M  As  reoenUr  studied  by  Balfour  (38, 80). 


,j».»«*:ft*<"!««WH3iSSK^ 


-*  i» 


*iiIR3re??*'^^^t. 


-, ;.:*:*«a(»aetiti  aer-.t 


IM 


B.     KATURAL  BISTORT. 


embryo  the  prothalamus  a  thin-walled  vescicle,  with  a  sinele 
^vity  which,  in  adult,  is  reduced  to  two  canals  diverging  forward. 
Prothalamus  remains  closed  forward  and  dorsad.  Nostrils  in 
pairs,  but  do  not  enter  mouth.    Cerebellum  folded  transversely. 

HoLOCKPHALi.  Brain  combines  characters  of  Selachians,  Ga- 
noids  and  Batrachians.  Crura  thalami  much  elongated.  True 
hemispheres,  larger  than  prothalami  or  olfactory  lobes.  Foramen 
of  Monro  very  large.  (The  last  two  sentences  have  been  added 
since  this  paper  was  read.    See  notes  31  and  36.) 

Ganoids.  Optic  ohiasma.  Rhythmically  contractile  bulbus 
arteriosus  with  several  rows  of  valves.  Hemispheres  rudimentary. 
Olfactory  lobes  sessile.  Prothalami  separate  forward  and  dorsad, 
and  more  or  less  everted.  Cerebellum  with  no  transverse  folds, 
foramina  of  Monro  large. 

Teleosts.  Optic  nerves  cross  but  form  no  chiasma.  Bulbus 
arteriosus  not  rhythmically  contractile  and  has  a  single  series  of 
valves.  Olfactory  lobes  sessile  or  pedunculated.  So-called  hemis- 
pheres  are  probably  prothalami;  more  or  less  everted  as  in 
Ganoids,  and  separate  forward  and  dorsad.  True  hemispheres 
rudimentary  or  absent.  Foramina  of  Monro  and  lateral  ventricles 
small  or,  perhaps  in  some,  obliterated.  (Last  sentence  added 
since  this  paper  was  read.) 

DiPNOANS.  Hemispheres  larger  than  olfactory  lobes.  Heart 
tnlocular.  True  nostrils.  Optic  chiasma.  (Should  probably  be 
^ranged  with  or  near  Batrachians  in  the  Series  of  air-breathing 

^  Batrachians.  Hemispheres  larger  than  olfactory  lobes.  Heart 
tnlocular.  Optic  chiasma.  No  corpora  striata  or  commissures. 
Walls  of  brain  thin  and  ventricles  large.    True  nostrils. 

Reptiles.  True  hemispheres.  True  nostrils.  Corpora  striata 
and  anterior  commissure.  Heart  tnlocular  or  quadrilocalar.  Right 
and  left  aortic  arches  persistent* 

Birds.    Same  brain  characters  as  in  Reptiles.    Heart  quadri- 


".t^3«a^_^■--- 


>*^  »  •>*    <    T^      .  ^  -  .       <-• 


1 


pith  a  single 
|rging  forward. 
Nostrils  in 
ransversely. 

Blachians,  Ga- 

^gated.    True 

Bs.    Foramen 

N  been  added 


actile  bulbus 
rudimentary. 
I  and  dorsad, 
isverse  folds. 


ma.    Bulbus 
gle  series  of 
sailed  hemis> 
erted  as  in 
hemispheres 
•al  ventricles 
tence  added 


hes.  Beart 
probably  be 
r-breathing 


•es.    Heart 
mmissuref. 


}ra  striata 
w.   Bight 


B.      NATURAL  BISTORT. 


187 


t  qaadri. 


looalar.    Right  aortic  arch  persistent.     (Birds  seem  to  be  an 
aberrant  group  of  Sauropsida.) 

Mammals.  Corpora  striata.  Anterior  commissure.  Corpus 
callosum.  Fornix.  Pons  varolii.  Heart  quadrilocular.  Left 
aortic  arch  persistent. 

By  characters  of  the  brain  alone  the  Ganoids  are  readily  sepa- 
rable from  all  other  vertebrates.  From  the  Teleosts  they  differ  in 
respect  to  the  optic  chiasma ;  also,  so  f  '  as  now  known,  on  ac- 
count of  the  greater  size  of  the  lateral  vwntricles  and  foramina  of 
Monro.^  But  differences  of  size  alone  are  not  reliable ;  and  our 
knowledge  of  the  structure  of  the  Tcleost  brain  must  be  much  ex- 
tended before  final  generalizations  can  be  made.  Meantime  it  is 
interesting  to  note  that  some  cerebral  characters  seem  to  associate 
the  Ganoids  with  the  Teleosts,  while  others,  with  cardiac  charac- 
ters, link  them  with  the  Selachians.  The  Teleosts  are  apparently 
dn  aberrant  group,  like  the  Birds. 

Minor  modifications  of  the  brain,  together  with  those  of  the  tail 
and  air-bladder,  will  probably  furnish  the  basis  for  subdivision  of 
the  Ganoids.  The  brains  of  Amia  and  Lepidoateua  are  very  nearly 
alike,  and  both  seem  to  agree  in  all  essential  respects  with  that 
of  Polypterua,  and,  by  inference,  CalamoicJithya.  The  brains  of 
the  Sturgeons  resemble  one  another  more  closely  than  they  do 
those  of  the  other  genera,  but  all  agree  in  the  rudimentary  hemi- 
spbece,  the  enlarged  prothalami,  and  the  position  of  the  foramen 
of  Monro. 

Reserving  for  the  present  any  discussion  as  to  the  separation  c' 
Dipnoans  from  Batrachians,  and  of  Birds  from  the  other  Sanrop 
sida,  the  groups  seem  to  readily  fall  into  five  categories.  The  first 
and  lowest  includes  Amphioxua  elone.  The  second  the  Myzonts 
and  Selachians,  whose  brains  are  differentiated,  but  bave  not. yet 
assumed  the  distinctive  features  of  either  the  true  aquatic  or  the 
aerial  Vertebrates.  They  have  the  form  and  habit  of  fishes,  but 
their  brains  are  more  readily  comparable  with  those  of  Batrar 
chiaus.  For  the  hemispheres  are  distinct,  though  small,  and  the 
thalamus  remains  closed,  instead  of  being  separated  forward  and 

>•  At  Uie  time  thU  paper  was  preMnted  I  had  not  been  able  to  And  these  openings 
In  any  Teleostean  brain,  and  therefare  supposed  that  their  existence  in  the  Ganoids 
ftkimed  a  sharp  distinction  between  the  two  groups. 


.\'<i'.':z:-:. 


-"■'i^ti^jaH  ■■fcj^^^^^^^^  *  ..^■'^^  "^ 


186 


B.      NATURAL   BISTORT. 


dorsad,  as  in  the  Telcosts,  the  Ganoids  and  Holocephali.  Ttie 
Holocephali  cannot  yet  be  fully  characterized.  The  brain  presents 
a  very  generalized  condition.  These  and  the  other  characters 
may  be  more  distinctly  presented  in  tabular  form. 


Series  V.  Hemispheres  well  de- 
veloped ;  larger  Ihau  olftictory  lobes. 
Pulmonary  auricle.    True  nostrils. 

Mammals. 

Birds. 

Reptiles. 

Batrachians. 

Dipnoans. 


Series  IV.  Hemispheres  rudU 
mentary  or  absent;  smaller  than 
olfactory  lobes.  Frothalamus  open 
forward  and  dorsad.  Dorsal  bor- 
ders of  prothalami  more  or  less 
everted.  Heart  bllocular.  Nostrils 
do  not  enter  mouth.      , 

Teleosts. 

Ganoids. 


Series  III.  Holocephali.  Brain  presents  a  condition  intermediate  be- 
tween Series  II,  IV  and  V. 

Series  II.  Hemispheres  distinct  but  smaller  than  olfactory  lobes.  Thal- 
amus not  open  forward  or  dorsad.  Heart  bllocular.  Nostrils  do  not 
enter  mouth. 

Selachians. 

Myzonts. 


Series  I.    Brain  not  differentiated  ftrom  medulla. 

Amphioxus. 


Heart  tubular. 


V; 


To  such  an  arrangement  of  vertebrates  as  the  above  the  palaeon- 
tologist would  naturally  object  upon  the  ground  that  it  includes 
no  osteological  characters  by  which  fossil  forms  may  be  collocated 
with  the  living. 

To  this  I  plead  gnilty,  but  urge  in  extenuation  the  following ; 

1.  The  argumentum  ad  hominem.  For  the  classifications  now 
in  vogue  make  little  or  no  reference,  or  that  of  the  most  unsystem- 
atic kind,  to  the  brain;  and  osteological  characters  alone  would 
not  enable  as  to  define  embryos,  Myzonts,  or  Amphioxus  at  all. 

2.  The  above  does  not  pretend  to  be  a  complete  or  final 
arrangement.  It  is  an  effort  to  show  how  far  cerebral  and  cardiac 
characters  concur  with  each  other  and  with  the  results  of  a  previ- 
ous consideration  of  all  systems  of  organs.  Such  an  effort  could 
hardly  be  successM  before  the  brains  of  fishes  were  structurally 
homologized  with  those  of  the  air  breathing  Vertebrates. 

3.  I  should  be  willing  to  have  it  shown  that  I  had  made  some 


V.f-i: 


B.      NATURAL  BISTORT. 


189 


focephali.    The 

brain  presentg 

Hier  characters 


Inilspheres  radl- 
Jtj  smaller  than 
pothalamus  open 
T8d.  Dorsal  bor- 
Jil  more  or  less 
|ocular.   Nostrils 


Pntermedlate  be- 


»ry  lobes.    Thai- 
Nostrils  do  not 


t  tnbnlar. 


^ethepalaon- 
»'  it  includes 
be  collocated 

following: 
ications  now 
8t  unsystem- 
alone  would 
fus  at  all. 
3te  or  final 
and  cardiac 
of  a  previ- 
>ffort  could 
tructurally 

nade  some 


mistakes  as  to  both  fact  and  interpretation,  for  the  sake  of  the 
advantages  which  I  am  confident  will  attend  the  careful  and 
systematic  reconsideration  of  our  present  methods  of  classification. 
These  last  are  almost  purely  empirical.  They  have,  as  in  the  case 
of  the  Ganoids,  led  to  the  most  diametrically  opposite  conclusions. 
Would  it  not  be  worth  while  to  enquire  whether,  from  both  analogy 
and  experience,  cerebral  and  cardiac  characters  are  not  more  trust- 
worthy  for  the  discrimination  of  larger  groups,  and  whether  char- 
acters drawn  from  the  skeleton,  teeth,  digestive  and  reproductive 
systems  are  not  likely  to  serve  us  better  if  restricted  to  the  deter- 
mination of  orders,  families  and  genera. 

When  the  limits  of  classes  and  sub-classes  have  been  once  as- 
certained by  the  study  of  the  heart  and  the  brain,  most  of  the  fossil 
forms  may,  by  the  correlations  of  their  hard  parts  be  assigned  to 
places  in  them.  At  present,  on  account  of  the  greater  availability 
of  hard  parts  for  preparation  and  preservation,  we  practically 
depend  upon  them  almost  entirely,  or  tacitly  assume  that  they  are 
of  greater  taxonomic  value  than  the  soft  parts,  and  that  the  latter 
are,  therefore,  readily  correlated  with  the  former. 

SuHHART.  1.  The  smallest  Lepidosteus  here  described  (18°™- 
long),  has  a  primordial  median  fln  extending  over  the  hinder  third 
of  the  body  above,  and  its  hinder  half  below,  interrupted  at  the  vent. 

2.  The  locations  of  the  dorsal,  the  anal  and  the  infra-caudal 
fins  are  marked  by  coloration  and  thickening  of  the  primordial  fin. 

8.  A  fourth  or  supra-caudal  fin  is  also  indicated,  though  less 
decidedly.    This  fin  is  not  functionally  developed. 

4.  The  tail  of  this  smallest  Lepidosteus  is  nearly  protocercal, 
the  end  of  the  body  inclining  ulightly  downward. 

5.  The  end  of  the  body  proper  is  gradually  forced  upward  by 
an  increase  of  the  infra-caudal  lobe,  and  becomes  the  "  filament " 
already  known  in  the  young  gar-pike. 

6.  The  movements  of  this  filament  are  extensive,  and  vibratory, 
and  wholly  voluntary. 

7.  The  filament  exists,  though  evidently  in  process  of  removal, 
in  a  young  Lepidosteus  osseus  300""-  long. 

8.  The  iniVa-caudal  lobe  becomes  the  functional  tail  of  the 
adult. 

9.  The  vertebral  column  is  then  continued  obliquely  upward 
and  backward  as  a  tapering  cartilaginous  rod  which  terminates  at 
a  point  corresponding  with  the  previous  separation  of  the  filament 


ii-i3&i.ri---JiBfc:- 


0^ 


U-s- 


190 


B.     HATDBAL   HIBTORT. 


ft-om  the  infVa-caudal  lobe.  This  point  coincides  with  the  hinder- 
most  of  the  dorsal  fulcra. 

10.  This  rod  comprises  the  notoohord,  the  spinal  cord  and  two 
lateral  cartilaginous  pieces. 

1?.  The  tail  of  the  adult  Amia  presents  a  similar  structure, 
excepting  that  the  rod  is  shorter  and  there  are  no  fUlora. 

12.  It  seems  probable  that  the  tail  of  Amia  passes  through 
stages  like  those  of  Lepidoateua,  but  the  smallest  specimen  here 
described  (70""^  long)  shows  no  sign  of  the  filament. 

13.  The  two  earlier  stages  of  the  tail  of  Lepidosteus  may  be 
compared  with  the  protocercal  (or  diphycercal)  and  the  ordinary 
heterocercal  tails  of  other  living  and  fossil  forms.  The  maaked 
heterocercal  tail  of  Amia  and  Lepidoateua  probably  existed  in 
Megalurua  and  some  other  mesozoic  forms,  but  is  not  known  among 
the  palffiozoic  fishes.  It  likewise  exists  in  the  embryo  of  certain 
Teleosts,  as  Oaateroateua  and  the  Siluroids. 

14.  The  pectoral  fins  of  Lepidoateua  attain  considerable  size 
before  the  appearance  of  the  ventrals. 

15.  The  latter  are  not  lobed,  but  the  former  consist  of  a  fleshy 
lobe  and  a  thin  fVinge  or  border. 

16.  In  the  smallest  Lepidoateua  the  branchiostegal  membranes 
are  separate  farther  forward  than  in  the  adult.  The  point  of  their 
Junction  in  the  young  becomes  a  transverse  fold,  which  may  cor- 
respond with  the  hinder  border  of  the  jugular  plate  of  Amia. 

17.  The  "foramina  of  Monro"  and  lateral  ventricles  have  been 
found  by  me  in  the  following  Ganoids :  — Amia,  Lepidoateua,  Aci- 
penaer  and  Polyodon;  and  in  the  following  Teleosts: — Perca, 
Scomber,  AnguUla;  in  Chimera;^  in  the  following  Selachians:  — 
Muatelua,  Carchariaa;  and  in  the  Myzont  genera  Myxine  and 
Petromyzon.  There  is  good  reason  to  believe  that  Scaphyrhyn- 
chua,  Polypterua  and  Calamoichthya  have  the  same  parts ;  and  that 
they  exist  in  other  Teleosts,  but  less  easily  seen  than  in  Ganoids, 
or  perhaps  wholly  obliterated  in  the  adults  of  some  species.  In 
both  Ganoids  and  Teleosts  the  fdramen  of  Monro  seems  to  open 
into  the  base  of  the  anterior  or  olfactory  lobe  on  each  side. 

18.  Aside,  therefore,  fi-om  the  difiierence  in  general  aspect  and 
in  size  of  the  foramina  and  ventricles,  the  Ganoid  and  Teleost 
brains,  as  heretofore,  are  most  readily  distinguished  by  the  cAuumia 
which  exists  in  the  former  group. 

"As  ttated  on  nrevloas  page*  the  foramina  wer*  found  In  CMmtra  and  tha  T*- 
leotU  aRor  thU  paper  waa  preaented. 


""''"iltililff'F ■' "  '   nn<ip  "I  I  I «> ■mil ii'iiiiiii  I 


.\i-" 


the  hinder* 

tord  and  two 

|ar  structure, 
Bra. 

8808  through 
ecimen  here 

fleua  may  be 
Ithe  ordinary 
I  The  nuuked 
existed  in 
Known  among 
yo  of  certain 

derable  size 

It  of  a  fleshy 

|I  membranes 
)oint  of  their 
lich  may  cor- 
'  Amia. 
'8  have  been 
iosteus,  Aci. 
ts: — Perca, 
lachians:— . 
Vyxine  and 
Scaphyrhyn- 
3 ;  and  that 
in  Ganoids, 
pecies.    In 
as  to  open 
ide. 

aspect  and 
id  Teleost 


B.      NATURAL  UIBTORT. 

19.  We  may  regard,  provisionally,  the  seven  genera,  Amia,  Lepi- 
dosteua,  Polypterua,  Calamoich''.^.,  Acipenser,  Scaphyrhynchua  and 
Polyodon  (together  with  such  fossil  forms  as  are  obviously  allied  to 
them)  as  constituting  a  natural  group  (class  or  sub-class)  charac- 
terized by  an  optic  chiaama;  a  rhythmically  contractile  bulbua  arteri' 
oaua  with  aeveral  rouia  of  valvea;  large  prothalami  aeparate  above 
byit  united  below;  rudimentary  hemispheres;  and  the  foramina  of 
Monro  opening  apparently  into  the  base  of  the  sessile  olfactory  lobea. 

20.  It  seems  probable  that  by  features  of  the  brain  and  heart 
alone,  all  of  the  primary  subdivisions  of  Vertebrates  may  be  accu- 
rately characterized. 

21.  The  Dipnoans,  hitherto  regarded  as  fishes  and  usually 
arranged  with  or  near  the  Ganoids,  agree  with  the  Batrachians  in 
cerebral  and  cardiac  and  other  characters.  This  group  seems  to 
furnish  a  case  for  testing  the  relative  tazonomic  value  of  charac- 
ters derived  f^om  the  brain  and  heart  on  the  one  hand  and  ftom 
the  skeleton,  limbs  and  digestive  organs  on  the  other.  In  like 
manner  the  brain  of  Holocephali  would  indicate  that  they  belon 
nearer  the  Ganoids  than  the  Selachians,  perhaps  as  a  transition 
between  the  two. 

21.  While  the  facts  and  considerations  presented  in  this  paper 
cause  me  to  doubt  the  correctness  of  all  classifications  of  fish-like 
Vertebrates  hitherto  proposed,  they  do  not  seem  to  Justify  the 
framing  of  another  system.  Nor  is  it  probable  that  any  phyllo- 
genetic  arrangement  can  be  proposed  which  shall  either  advance 
science  or  reflect  credit  upon  the  propounder,  until  our  knowledge 
of  the  embryology,  of  the  brains  and  of  fossil  forms  is  much  more 
extensive  than  at  present.^ 

Appendix. — Just  as  this  goes  to  press  I  have  been  able  to  oon« 
suit  the  admirable  paper  of  Paul  Langerhans,  *'Untersuchungen 
nber  Petromyzon  Planeri,"  pp.  114,  16mo,  10  Tafeln.  Freiburg, 
1873.  This  author  figures  and  describes  (p.  83)  the  lateral  and 
olfactory  ventricles  of  Petromyzon.  He  also  states  (p.  95)  that  an 
optic  chiasma  does  exist.  These  statements  must  be  considered  in 
connection  with  paragraphs  upon  pages  178,182, 185  of  this  paper. 

1  As  this  paper  li  psMing  throngb  the  pr«M,  I  bare  seen  in  the  ■■  Zoological  Beeord" 
for  1873.  page  86,  an  abstract  of  a  memoir  by  Panoeri  and  De  Sanctis  "  Sopra  alounl 
organl  delta  C^halopttni,  Napoli,"  1860, 4to.  The  authors  recognise  font  types  of  brain 
besides  that  in  AmpkU>xu$  i  namely,  in  Cydostomata ;  in  Teleosts  ;  in  fonr  Selachian  gear 
•ra,  JHetrobatU,  Xygana,  MtUobatU,  n-ygon  i  and  in  all  other  Selachians  and  Ganoids. 

No  mention  is  made  of  the  lateral  venfc'iclea  or  foramina  of  Monro,  and,  so  Ar  aa- 
in<Uoated  by  the  abstrast,  the  conolosions  are  VerydUTerent  from  those  here  presented. 


iiiiHi'l 


■•mIIm 


1/ 


tt^mtmr^ 


192 


.-J 


B.      NATUBAL  niSTOBT. 


WOllKS  AND  PAPBaS  REFEIUIED  TO. 

1.  AoABRiz,  Louis  :  Lake  Superior ;  It*  phy deal  character,  Tegetat.jn,  and  anl- 
malt.    pp.  428;  H  plates.    Boaton,  IDAO. 

2.  AuAHSiz,  La:  Young  gar-plkot  from  Lake  Ontario.  (Proceetlingi  Boiton  aoo. 
nat.  hilt.,  18MI;  vl,  48.) 

8.  AOAHSTZ,  Lh  :  ObFurrntion*  sur  let  metamorphosei  des  poliioni.  (Ann.  dut  lol. 
nat.  1805.    Ill,  6S-58.) 

4.  Oi'MftiiiL,  A.:  Illstolre  nat.  de«  polttont.  (Qanoldei,  DIpnoani,  Lo|itiu- 
branolies)  8vo,  pp.  023.    Flrtnchea. 

5.  A0A8SIZ,  Louil :  Uooliercbea  lur  lei  potaioni  fosallc*.  183S-1840.  4  rnlumea, 
quarto. 

fl.  IIuxLBT,  T.  H. :  Prellrolnarv  etsny  upon  the  Ryttematlo  arrangement  of  ttie 
flihos  of  the  Devonian  epoch.  (Memolra  of  the  geological  surTcy  of  the  United 
Kingdom.    Decade  x,  1861.) 

7.  lIuxLBr,  T.  H.  1  Manual  of  the  comparative  anatomy  of  vertebrated  anlmali. 
N.  Y.,  1872. 

8.  IIUMriiRiiY,  O.  M. :  On  the  homologlcal  relations  to  one  another  of  the  mesial 
and  lateral  lint  of  osseous  llshus.  (Journal  of  anatomy  and  physiology,  Nov.,  1870, 
09-06.) 

9.  AoASSiz,  L. :  Notice  of  a  collection  of  flshot  ft-om  the  southern  bend  of  the 
Tennessee  River.   (Am .  Joum.  of  science,  new  aeries,  No.  2L    SSS-SOS.) 

10.  Franqux,  Hrnricus;  Amisa  calvK  anatomlam  descrlpkit  tabulaqne  lUut- 
travit,  (bllo,  pp.  12;  1  plate.    Berlin,  1847. 

11.  Wyman,  Jeffries:  Observations  on  the  development  of  Andi  ioM*.  (Memoirs 
of  American  academy  of  arts  and  sciences,  Jun.  27, 1874.)    44  pages  quarto,  1  plate. 

IS.  QiLL,  Theodore:  Arrangement  of  the  flimlllet  of  Flibet.  (Smithsonian 
miscellaneous  collections.    [274],  1872.) 

13.  QooDBiR,  JoiiN :  Anatomical  memoirs.  8vo,  3  vols.  pp.  903,  many  plates  and 
flgures.    Edinburg,  1^. 

14.  OEOBNBAim:  Grundrist  der  verglelchende  Anatomic.  8vo,  pp.  4Ct),  320  flgnret. 
Leipzig,  1874. 

15.  Huxlet,  T.  H.:  ObserTationa  on  the  development  of  the  tall  In  Teleostcan 
flshet.    (Quart.  Journal  of  microscopical  science,  vii|  33-44;  plate  HI.    18M>.) 

16.  LtlTKEN,  C. :  On  the  limits  and  classification  of  the  Uauoidt.  (Translation.) 
(Annals  and  magazine  of  natural  history,  May,  1871.   320-330.) 

17.  Cope,  E.  D. :  Observations  on  the  systematic  relations  of  flshet.  (Proceedings 
Am.  asso.  for  adv.  of  science,  1871, 317-343.)  [Preliminary  publication,  slightly  different, 
in  American  naturaltsi,  1871, 579-506.] 

18.  MOller,  Johannes:  Ueber  den  Baa  nnd  die  Grenzen  der  Ganolden  und  Uber 
das  natilrliche  System  der  Fische.  ( Abhandling  der  KttnigUchen  Akademie  der  Wistent- 
chanen  zu  Berlin,  1844.    4to,  117-216,)  16  plates. 

19.  GOhther,  Albert:  Description  of  Ceratodut,  a  genus  of  Ganoid  flshea  re- 
cently discovered  In  the  rivers  of  Queensland:  Australia,  (Pbllosphical  transaotlont, 
1871,511-571.   42  plates.) 

20.  AOASSIZ,  Louis :    A  journey  In  Brazil,  8to.,  pp.  540.    Illustrated.  1868. 
81.    AOASBiz,  L. :    An  essay  on  clarsiflcation.    6vo,  pp.  381,    London,  1850. 

22.  AoASSiz,  Louis  :  The  clatslfication  of  the  Silurold  flshet.  (Proc.  Boston  too. 
nat.  hist.,  Dec.  18, 1868.   p.  864.) 

23.  W YUAN,  Jeffries  :  Anat'omyof  the  aervous  system  of  Aana  ptfrfm*.  (Smith- 
sonian contributions  to  knowledge,  v,  ait.  4, 1855,  quarto,  pp.  51.   2  plates. 

84.  Owen,  Richard:  Comparative  anatomy  and  physiology  of  vertebrates,  3 
volumes,  8vo,  pp.  2155.    1471  flgures.    London,  1861-1868. 

85.  Owen,  R.:  Description  of  Zepidcriren  ( Protopterui)  anntetem.  (LInnaan 
transactions,  xviil,  827-381).,  5  plates. 

86.  Newberry,  J.  8.:  Description  of  fossU  flshet  of  Ohio.  pp.  110,  17  plates, 
(Geological  survey  of  Ohio.   Vol.  1, 1878.) 


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"§ 


NATURAL   HISTORT. 


193 


IT.  PoiT,  r. :  Observations  on  lUfforont  points  In  the  natural  hiatorx  of  Cuba. 
(Annals  of  the  lyreum  of  nnt.  hist.    N.  Y.,  1858.    vt,  ISO.) 

S7,  WiLDP.R,  B.  U. :  The  lateral  position  of  the  vent  In  AmphU>xui  and  In  certain 
batrachinn  larra).    (Proc.  Am.  asso.  for  adT.  of  science,  1873.)    pp.  'i.\  10  llgureii 

38.  MULi.Kn,  J. :  nerlcht  Uber  die  KorUtihrltto  dor  verglelchenden  Aoatomie  der 
WIrbelthloro  In  Jahro,  1841.    (Arohir  nir  Annt.  18«i;  coxxxvlll-cdxl.) 

M.    Buscil,  W. :    Oe  Selnchloruin  et  ganoldeorum  eniiephulo.    4to;  1818. 

80.  aoTTROHB,  C.  M.:  Vorgl.  Anat.  des  Ouhlms  der  Oratonflscho.  (Arrh.fUr  Anat, 
ISM;  m-^H,  488-486;  Taf.  Iv  und  vl.) 

31.  VuLi-iAN,  A.:  Lofons  sur  la  physlologie  g4n<rale  et  comparutlTe  du  systome 
nerveux.  1H«II;  8to;  pp.  M. 

3*.  Stanmius,  H.  :  Uebor  den  Dau  des  Oehlms  des  StOrs.  (Archlv  rUr  Anntomie, 
1848,30-41;  tnf.  Ill,  H.) 

33.  Valkntik;  Uebor  das  centrale  Nerreiiiystem  und  die  Nebenhorzen  dor  Chi- 
mara  moiutroia.    (Arch.  fUrJVnatomie,  1848,  W-4S.    Taf.  II.) 

84.  HoLLARD,  II. :  Recherohes  aur  la  strncturo  de  I'enciphnle  des  polssons  et  sur  la 
slgnlflcntlon  homologlque  de  ses  dlir4rentos  parties.  (Robin's  Jonmal  de  I'auatomie, 
I860.  a86-aas,  pi.  v-viii.) 

36.  TiBUEMAMM,  F.:  The  anatomy  of  the  footal  brain;  with  a  comparative  exposi- 
tion of  Its  structure  In  animals.  English  translation,  pp.  334;  14  plates.  Edinburgh, 
18M. 

86.  MUller,  Joiianmrs  :  Ueber  den  elgenthUmllchen  Bau  des  GehUrorganes  bel 
den  Cyvlostomen,  m!t  Uemerkungen  Uber  die  uuglelche  Ansblldung  der  SInnesorJane 
bet  den  Myxinolden.  pp.  St.  Taf.  1-3.  (Abhandlungon  der  KiinigUulien  Akadomte  der 
Wissenschaften  zu  Berlin,  1837.) 

87.  MCllku,  Johannes:  Vorglelchende  Neurologle  der  Myxinolden.  pp.8.  (Abh. 
der  KOnigl.  Akad.  lu  Berlin,  1838.) 

ar    CUSLAMD,  John:  Anlmalphyslology;  the  structure  and  ftmctlons  of  the  human 

bod^\      London  and  New  York,  1878. 

38.  Balfour,  F.  M. :  Development  of  the  uro-genlt«l  organs  of  vertebrates.  Journal 
of  anat.  and  physiology  vol.  x,  part  1, 1875. 

40.  Mayer,  F.  J.  U. :  Ueber  den  Bau  der  Oehlms  Fische  In  beziehung  auf  eina 
daranf  gegrUndete  EIntheilung  dleser  Thiorklasse.  Mlt  sleben  Stelntafeln :  pp.  40. 
(Novomra  Actorum  •••  Natural  Curiosorum.   Tom.  VIcesimus  Secundns.    1864.) 

41.  MOller,  J. :  M«molre  sur  les  Oanoldes  et  sur  la  classiflcation  naturelle  des 
polssons.  Translated  from  WIegtnann's  Archives,  1845.  (Annates  des  soleucos  natu- 
relies.    Sme  series,  tome  xiv.    184n,  B-53.) 

42.  VooT,  Carl:  Quelques  obiiervatlons  sur  les  caractires  qui  servent  a  la  olassl- 
flcatlon  des  polssons  ganoldes.  (Aiinalos  des  sciences  natureUes,  t.  xiv,  1846,  £3-08; 
with  1  plate.) 

43.  Foster  and  Baltoub  ;  The  elements  of  embryology.  )6mo,  pp.  S72, 71  figures* 
London,  1874. 

44.  LAN0ERHAN8,  Paul:  Zur  Anatomic  des  .^mpfcioruf  tonoeoloiti*.  (Arohiv  fllr 
kroskopisobe  Anatomie,  Band  xli,  sweltes  heft,  1875;  pp.  290-348;  Taf.  xil-xv.) 

45.  Miklucho-Maclat.  Beitrag  zur  verglelchenden  Anatomie  des  Gehlrns.  pp. 
19, 8  fig.    (Jenalschen  Zeitscbrift  fUr  medlcin  und  Natnrwisgenschaft.    1868.) 

46.  GUnthbr,  A. :  C«ra<odu«  and  its  place  in  the  system,  pp.  5,  3flgs.  (Annals 
and  magazine  of  natural  history,  1871.    vii,  232-227.) 

47.  HUXLBT,  T.  H. ;  On  Ceratodtu.  (Proceedings  xoOl.  soc.  London,  Jan.  4, 18T6.) 
[Mentioned  in  "  Nature,"  Jan.  6.] 

48.  AOA88IZ,  Louis:  Contributions  to  the  natural  history  of  the  United  States; 
quarto,  4  vols. 


A.  a.  VOL.  XXIV. 


(18) 


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EXPLANATION  OF  PLATE  !.*• 

lif .  1.  Toang  l^UloUtui  19»-  In  length,  enUrged  S  diameters.  The  tip  of  the  tall 
It  milling,  and  Itt  luppoaed  form  li  indicated  by  the  dottod  outline.  N,  the  noitrlU 
of  the  left  aide;  the  anterior  one  li  more  nearly  upon  the  upper  lurfhoe  than  In  the 
•dult.  In  the  margins  of  the  Jawi  appear  alight  elevations,  probably  teeth.  O,  the 
operculum ;  />,  the  pectoral  fln  conilating  of  a  rounded  fleahy  lobe  £  and  a  thin  lyinge 
/*;  1 , 9, 8, 4,  S,  regions  of  the  primordial  median  fln.  V,  the  vent.  C,  the  commencement 
Of  the  InfVa-oaudal  lobe.  The  commencing  anal  la  seen  between  T,  audi'.  Z>,  the  com* 
nenctng  dorsal  fln;  X,  indicates  a  slight  and  transitory  modiflcalion  of  the  primordial 
fln  like  a  aecond  doraal,  or,  more  probably,  aupra-caudai  lobe.  The  ventrals  have  not 
appeared.   The  lines  above  flgurei  1, 1, 8  Indicate  the  actual  length  of  the  young  Ltpi- 


Tig.  9.  Tall  of  young  ttptdciteui  29"-  In  length,  enlarged  4  diameters.  The  letter* 
ingaslnflg.l.  Theinfr..  3audal(C)  begins  to  project  beyond  the  outline  of  the  primor* 
dial  fln.    V«  the  ventral  fln. 

Fig.  3.  Tnllofyottng£fpMo«<«iui44'W'in  length, enlargodldiameters.  Letteringaa 
in  flg.  9.  The  primordial  fln  exists  pnly  upon  the  borders  of  the  filamentary  tormina* 
Uon  of  the  body  {ti)  which  Is  now  crowded  up  by  the  increasing  inftra-oaudal  lobe. 

Fig.  4.  Tail  of  young  LepidoiteH*  niitui  WOf*-  long,  natural  site.  The  Infl-a-oaudal 
lobe  now  occupies  Its  permanent  place  as  the  flinctlonal  tall,  while  the  fllament  ( Fi) 
bat  nearly  disappeared.  Its  base  is  protected  by  six  pair  of  fUlcra  {DF)  and  a  similar 
Mrlet  covert  tLo  anterior  half  of  the  lower  border  of  the  tall  ( VF). 

Fig.  8.  Dissected  tall  uf  medium  sized  £«p.  platyitomut.  The  fllament  has  disap* 
peared  and  the  (Ulora  extend  backward  to  a  point  nearly  corresponding  with  Its  sepa- 
ration from  the  caudal  flu.  'To  this  point  may  be  traced  a  cartilaginous  rod  (H),  the 
prolongation  of  the  vertebral  column  ( VC),  and  previously  continued  into  the  fllament. 
This  rod  consists  of  the  notochord,  the  spinal  cord  (5(7),  and  a  cartilaginous  sheath. 
NC,  neural  canal  laid  open.    HC,  hamal  canal,  laid  open. 

Fig.  6.  Section  of  the  upper  margin  of  the  tall  of  L.  platyitomui  at  a  point  about 
mid-way  between  the  base  of  the  fln  and  the  last  pair  of  fUIcra;  enlarged.  Jf,  noto* 
ehord;  SC,  spinal  cord;  CS,  cartilaginous  sheath,  in  which  the  vertebra  are  afterward 
developed.  F",  points  of  the  upper  nilora;  F*,  cut  surfaces  of  the  next  lower  fUlcra; 
F,  cut  surfaces  of  the  lowest  ftalora  which  are  separated  so  as  to  embrace  the  upper 
half  of  the  cartilage.  CJt',  cut  surface  of  the  uppermost  caudal  fln  ray,  the  two 
halves  being  separated  above  to  enclose  the  lower  part  of  the  cartilage.  The  dark  line 
ijrossing  the  section  Indicates  the  commencing  splitting  of  the  ray  Into  two.  CR,  the 
halves  of  the  second  fln  ray  not  quite  perfectly  apposed,  and  Joined  by  a  double  mem- 
brane to  the  rays  above  and  below. 

••AU  the  flgnret  were  drawn,  ttom  tpeciineni  and  preparatlont,  by  Mr.  Philip 
Barnard. 

(194) 


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l-'iu;>  I.     ViMiiiK  Li'l'lil'i"!''!!'.  I'lilitrw'')  ■<  illiiiiiuli  !''< 


KIk-  i'    Tail  or  yoiiiiK  l.<>|>li|i>nluiH,  oiiIiii'k<'<I  I  (llitiiiotoin 


V\g.  3.    T.'"  of  yuiiiitc  l,0|ii<lo»loiiK,  I'lilai'Ktxl  i  illiiiiictiM'H 


Vig.  4.    Tail  i>r  young  LeiiUloHtoiis,  naliintl  hIzd 


*,f4 .,  .-^v*- 


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two  diameters. 


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Fig. ».    Aciponser. 


Fir 


Fig.  10.    Polyodon. 


Kig.  1 1.    Cross  soctlons  of  PvotbtUmi  of  Ganoids. 


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EXPLANATION  Of  PLATE  II. 

Fig.  7.  Vertical  longitudinal  lection  of  the  brain  of  LepidotI  u  o$ieu$.  Tlie 
ipecimen  was  a  female,  about  four  and  one-hnlf  feet  long.  The  i  ure  is  enlarged 
two  diameters.  The  cut  surfaces  are  dotted.  SC,  spinal  cord;  AT,  medulla  oblongata; 
IV,  fourth  ventricle;  (76,  cerebellum ;  CK,  ventricle of4be  cerebellum;  1,  anteverted 
posterior  border  of  the  cerebellum;  behind  this  is  seen  the  low  ridge  referred  to  in 
the  text;  AS,  aqueduct  of  Sylvius,  or  passage  ft'om  the  fourth  ventricle  into  that  of  the 
optic  lobes;  0£,  optic  lobe;  OK,  optio  ventricle;  C,  conarium  or  pineal  body  Justin 
front  of  the  opening  of  the  optic  ventricle;  ///,  third  ventrM|openiug  downward  into 
the  hypoaria  or  lobi  inferiores,  which  may  represent  the  vPpora  einerea  of  anthro- 
potomy ;  2,  the  thickened  hinder  wall  of  this  cavity ;  3,  the  hypophysis  or  pituitary  body, 
apparently  vascular  and  easily  detached ;  n  narrow  longitudinal  slit  communicates  with 
the  cavity  above;  4,  the  optic  chlasma,  farming  part  of  the  anterior  wall  of  the  hypoa- 
rian  ventricle;  ON,  the  right  optic  nerve;  PTH,  the  right  prothalamus  (usually  called 
hemisphere) :  6,  commissure  connecting  the  prothalami ;  it  is  connected  with  the  optie 
chlasma  by  a  thin  lamina  forming  part  of  the  floor  of  the  ventricle;  FM,  the  foramen 
or  Monro;  H,  a  raised  margin  of  this  oriflce,  which  is  more  apparent  in  the  other 
brains,  and  may  be  a  rudimentary  hemisphere;  OIL,  oldactory  lobe,  containing  a  veu< 
tricle  which  communicates  through  the  foramen  of  Monro  with  the  third  or  median 
ventricle  between  the  prothalami  of  opposite  sides.  In  Amia,  AHptnier  and  Polyodon 
the  optic  lobe  Is  connected  with  the  prothalamus  by  a  lower  rounded  cms  thalami  on 
each  side;  but  as  the  ganoid  nature  of  those  genera  is  denied  by  some,  I  chose  the 
brain  of  Ztpidotteut,  although  it  is  less  well  adapted  to  display  all  the  parts. 

Figs.  8, 9, 10.  Mesial  surface  of  the  right  olfactory  lobe  and  nerve,  the  hemisphere, 
foramen  of  Monro  and  anterior  part  of  the  prothalamus  of  Amia,  Aeipeiuer  and  Poly- 
odon;  enlarged  two  diameters.   The  letters  as  in  Fig.  7. 

Fig.  11.  Transverse  sections  of  the  prothalami  enlarged  two  diameters.  These 
figures  are  somewhat  diagrammatic,  but  they  indicate  the  facts  that  the  lateral  masse* 
(O  are  solid,  with  dorsal  borders  (D)  more  or  less  everted,  so  as  to  form  anr  external 
concavity  (£);  that  they  are  connected  by  a  ventral  commissure  (B)  and  that  between 
them  (^)  is  a  space,  the  median  or  third  ventricle.  5,  Polypttrut  (fl-om  MUller);  3, 
Amia!  i,  young  Amia,  70°>»'  in  length ;  1,  Lepidotteui  osaeus;  3,  young  Lepidotttut, 
800»«'  in  length;  6,  Polyodoni  7  and  8,  ^<Kpent«r  ruMcuiuitis,  at  two  different  point* 
and  angles. 

(196) 


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EXPLANATION  OF  PLATE   III. 


n  tended 


and  in  transverse  sections  tliroagti  several  parts.   Tlia 


Fig.  12.   Diagrams  Inte^ed  to  represent  the  structure  of  a  ganoid  brain  as  seen 
in  longitudinal  mesial  se 
letters  as  in  Fig.  7. 

Fig.  13.  Diagrams  representing  the  cross-section  of  the  prothalami  of  Myzonts  (if) 
and  Selachians  and  of  the  hemispheres  of  Batrachians.  The  prothalamns  of  the  adult 
Myzont  is  closed  above,  as  in  the  embryo  Selachian  (£5).  In  the  adult  Selachian,  by  a 
deposition  of  matter  the  single  cavity  is  fliled  up,  excepting  two  lateral  canals  which 
converge  backward  to  meet  opposite  the  optic  foramen,  and  diverge  forward  to  enter 
the  olfactory  crura  through  the  small  hemispheres.  In  Ganoids,  as  seen  in  Fig.  11,  the 
prothalamus  is  open  above.  Likewise  in  many,  if  not  all,  Teleosts,  in  which,  however, 
the  optic  nerves  form  no  chias^na.  In  Batrachians,  as  in  the  Dipnoans,  the  place  of 
the  prothalami  is  taken  by  a  pair  of  true  hemispheres,  each  containing  a  lateral 
ventricle. 

Fig.  M.  Anterior  part  of  prothalamns  of  a  perch  (Perea  flave»een$),  with  the  olfac- 
tory lobe  and  nerve,  and  the  small  foramen  of  Monro.  (The  dotted  line  makes  the  ven. 
tricle  larger  than  it  is  really.)  Enlarged  ten  diameters.  The  existence  of  the  foramen 
in  some  Teleosts  was  ascertained  after  the  paper  was  read.    See  page  184. 

Fig.  15.  Diagrams,  slightly  altered  trom  Huxley,  to  indicate  the  typical  structure  of 
the  brain  in  Batrachians,  Iteptiles,  Birds  and  Mammals.  The  upper  is  a  liorizontal,  the 
lower  a  vertical  section.    See  page  17t. 


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